Helmets

- In-molded construction - TransTextura moisture-wicking, anti-odor inner padding - MIPS Protection - Optional visor on Path MTB helmet Sizing: - Small/Medium = 49 – 57cm - Medium/Large = 53 – 61cm

Premium features, certified protection, and sleek styling make the Chamonix a tremendous value for any cyclist. You'll also find that it's equipped with next-level protection courtesy of revolutionary MIPS technology (Multi-Directional Impact Protection System). - One-size system, designed for an easy and accurate fit to a wide range of head sizes - Headset SX fit system with micro-adjustable dial for an easy, secure, and accurate fit - 4th Dimension Cooling System optimizes ventilation - In-molded shell improves strength and reduces weight - Tri-Fix web splitter for improved comfort and ease of strap adjustments - Reflective webbing and decals for increased visibility to motorists in low-light conditions - Patented clip-on visor included - MIPS-equipped - Fit system is ANGi crash sensor ready

The trails are calling. An off-road, all-purpose helmet, with sixteen air-vents for comfort and a lightweight design, perfect for every trail and adventure. Where it thrives: Challenging trails, up and down hills What it's built for: Comfort, durability Highlights: - Extra rear coverage reflective logos - 16 air vents / one-piece visor - One-handed adjustment for easy fitting

With a sleek and fast look, the Echelon helmet presents a compact profile on a rider's head. And with increased ventilation and an ergonomic design, you're guaranteed an exceptional fit, tremendous comfort, and ample ventilation. Accordingly, it's the ideal helmet for road cycling enthusiasts. - Easy-adjust Headset SL II fit system with six height positions and micro-adjustable dial - 4th Dimension Cooling System optimizes ventilation - Composite matrix internal reinforcement allows larger vents for greater cooling - Tri-Fix web splitter for improved comfort and ease of strap adjustments - Reflective decals for increased visibility to motorists in low-light conditions - MIPS-equipped - Fit system is ANGi crash sensor ready

Loosely based upon the leather "hairnets" that cyclists used to wear before protection was a priority, we took their ventilation and classic style and incorporated them into a modern helmet design that combines aerodynamics, weight, aesthetics, and ventilation—the Airnet with MIPS. - Ultra-light Mindset micro-dial fit system with height adjustability for the perfect fit. - 4th Dimension Cooling System with deep internal channels, large vents, and aligned exhaust ports. - Composite matrix internal reinforcement allows larger vents for enhanced cooling. - drirelease Merino wool pads for increased comfort and sweat/ temperature management. - Vent grippers integrated at the front and rear for secure eyewear storage. - Thin, soft, and lightweight 4X DryLite webbing won’t stretch out with sweat or water. - Tri-Fix web splitter for improved comfort and ease of strap adjustments. - Instrap webbing system for ultra-light construction and security. - Reflective decals for increased visibility in low-light conditions. - MIPS-equipped.

As bikes become more capable and trail riding gets faster the M2 slots into the current generation of open face protection. Conehead technology utilises dual-density foam to dissipate impacts more effectively giving you a safer ride. The Boa Fit System delivers a connected, fast, customized and durable fit, purpose-built for performance. - 19 vents provide cool air intake and heat exhaust - Conehead technology - Full rear head coverage - Custom 7iDP liner for superior fit and comfort - BOA one hand dial fit adjustment - Rapid adjust chin strap - Tested beyond CE, CPSC, AS standards The M2's foam liner is made of two density layers. The outer layer, which is the black part, is made of high-density foam and has cones facing inwards. The inner layer, the grey part which is close to the head, is made of softer low-density foam and has cones facing outwards.

- Open face all mountain design - 19 vents - ConeHead Technology utilizing dual density foams in impact absorbing zones - Full rear coverage - Boa one hand dial fit adjustment - Adjustable visor - Rapid adjust chin strap - Certified : CPSC Bike Sizing: - X-Small/Small = 52 – 55cm - Medium/Large = 56 – 59cm - X-Large/XX-Large: 60 – 63cm

Anywhere, any day. A true go-anywhere helmet with a low-profile lightweight design, extra rear coverage, and a mini visor for a relaxed, modern look for all rides. Where it thrives: Gravel roads, the open road, up and down hills What it's built for: Comfort, durability Highlights: - MIPS equipped and extra rear coverage for increased protection - 23 air vents / one-piece visor - One-handed adjustment for easy fitting

When ripping down the trail, the last thing you need to worry about is if your helmet will protect you in a crash. Then again, you don't want to be stuck wearing a full-face on every trail ride. This is why we created the Ambush, the lightest and most ventilated extended coverage helmet available. We've teamed up with MIPS researchers to introduce MIPS SL—a new, ultra-light, and supremely comfortable version of MIPS that's available exclusively on Specialized helmets. With MIPS SL, we've essentially integrated MIPS technology within the helmet padding itself. MIPS SL's minimalist "watchband" attachment system provides 10 to 15 millimeters of rotation in every direction and offers the same brain protection benefits as other versions of MIPS, while also ushering in a new level of comfort and weight savings. Starting with protection, the Ambush boasts a significant amount of extended coverage, Energy Optimized Multi-Density EPS foam that manages the energy from impacts effectively, and a Aramid-Reinforced Skeleton that provides extra structure for the foam. Even with the added protection, though, it fits comfortably with our low profile and fully integrated Mindset 360 fit system. With its five height positions, this system provides unmatched adjustment, while an integrated dial allows for on-the-fly tinkering. The Ambush also keeps you cool with our 4th Dimension Cooling System's massive vents and exhaust ports, so you don't have to worry about overheating—even on the hottest days. Finally, we included a micro-indexing visor that quickly adjusts positions and has plenty of room for goggle storage. Combined, these features put the Ambush well in front of the competition. Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older. - New MIPS SL is the lightest, most ventilated MIPS protection to date and is exclusively available on Specialized helmets. - Patented aramid-reinforced skeleton provides internal EPS support. - Patented Energy Optimized Multi-Density EPS construction helps to manage impact energy. - Mindset 360 fit system provides a secure, customizable fit with 360-degree tension adjustment, five height positions, and an integrated dial for easy, on-the-fly adjustments. - Micro indexing visor allows for a wide range of fast, secure on-trail adjustments, as well as convenient goggle stowage. - 4th Dimension Cooling System with massive vents, internal Cross-Channels, and aligned exhaust ports increases airflow to keep you cool. - Low profile in-molded shell with smooth, snag-free exterior shape. - Extended coverage for added protection and durability. - This helmet is ANGi ready, with a fit system mount designed for easy integration with our ANGi crash sensor. - Our available aftermarket ANGi sensor gives you and your loved ones peace of mind like never before. When combined with our Specialized Ride app, the ANGi sensor will evaluate the forces acting on the helmet in the event of an accident and, if necessary, send a text message to your specified contacts with your location. - Lightweight, quick-drying liner features a Gutter Action Brow that channels moisture away from eyes. - Tri-Fix web splitter for improved comfort and ease of strap adjustments.

The Network helmet is the perfect blend of style, versatility and performance. Cyclists will welcome the clean, modern design combined with the superior protection and ventilation properties that only Koroyd can provide. Koroyd is featured in strategic, zonal impact areas offering increased protection where it matters most. As eyewear integration is mandatory for this rider, the AirEvac system works to pull air off of your eyewear to prevent fogging. Pass-through channels allow eyewear to be easily stored on the front of the helmet. - Lightweight Aerocore in-mold construction - Ventilated protection featuring patented Koroyd material - MIPS system available in all colors - VaporFit adjustable fit system - 20 optimized vents - XT2 anti-bacterial performance lining - Ultra-light single layer webbing - AirEvac ventilation - Camera and light mount compatible - Ultimate sunglass integration - Adjustable/removable visor - Weight (Size M) 10.58oz / 300 grams - Certification: CPSC, CE EN 1078 Sizing - Small: 51 – 55cm - Medium: 55 – 59cm – Large: 59 – 62cm

ALLL-ROUND HELMET The Macator is a sporty entry-level helmet for cyclists looking for an outstanding all-round helmet. The Macator has not only a comfortable padding but also offers an excellent ventilation, and it comes in a variety of bright, highly-visible colors. In-Mold: Lightweight, durable helmet with a long-lasting combination of EPS core and Polycarbonate shell - Bug mesh: Full protection from insects - Ponytail compatibility: Perfect fit for people with long hair - Full-ring: Adjustable ring connected to adjustment system enclosing all of the head - Excellent ventilation with 5 air inlets and 8 air outlets - Zoom Ace: Finely adjustable adjustment system with handy adjustment wheel for customizable fit

The Macator is a sporty entry-level helmet for cyclists looking for an outstanding all-around helmet. The Macator not only has comfortable padding but also offers excellent ventilation. - In-Mold: Lightweight, durable helmet with a long-lasting combination of EPS core and Polycarbonate shell - Bug mesh: Full protection from insects - Ponytail compatibility: Perfect fit for people with long hair - Full-ring: Adjustable ring connected to adjustment system enclosing all of the head - Excellent ventilation with 5 air inlets and 8 air outlets - Zoom Ace: Finely adjustable fit system with handy adjustment wheel for a customizable fit Sizing: - Medium: 51-55cm - Large: 52-58cm - X-Large: 58-62cm

With cutting-edge design and maximum ventilation, Rev is one of the official helmets of Team CCC. From hors categorie climbs to World Cup cyclocross racing, it’s the ultimate choice for superior fit, comfort, and protection. - 21-vent configuration for optimal airflow and top-of-the-head ventilation - LiteForm webbing for enhanced comfort and performance - Internal Structural Shell (ISS) for strength at a reduced weight - Giant CINCH+ fit system for simple and easy head-hugging comfort - Proprietary TransTextura PLUS anti-microbial fast-wicking pad technology - MIPS is a low friction layer between the head and the helmet that provides added protection with respect to angled impacts

- In-molded construction - TransTextura moisture-wicking, anti-odor inner padding - MIPS Protection Sizing: - Small/Medium = 49 – 57cm - Medium/Large = 53 – 61cm

One helmet all road. The MET Allroad Mips is made for those who enjoy spending time on the saddle, whether on the tarmac or on gravel routes. Sporty on one side, comfy on the other. It's exceptionally lightweight and secure thanks to MET's distinguishing design. Perfect for your next bikepacking adventure. Featuring the MIPS-C2 brain protection system, the MET Allroad Mips is able to slide relative to the head in the case of a crash, redirecting damaging rotational motion. - In-mold polycarbonate shell with EPS liner - MIPS-C2 Brain Protection System - Snap in/out visor - Safe-T E-DUO Fit System - Vertical adjustment and ponytail-compatible - Integrated rear LED light - Reflective rear stickers - Internal air-channeling - Hand washable comfort pads - Adjustable cam divider - Certifications: CE; AS/NZS

Integrated for speed. Pursuit combines the aero speed of a TT helmet with the head-cooling ventilation of a pro road racing helmet. Tested and proven by Team Sunweb riders like Michael Matthews, who wore it to win the 2017 Tour de France points classification, Pursuit brings together innovative technologies to optimize aerodynamics, ventilation and comfort, all in one helmet. FEATURES - Optimized ventilated aerodynamics design - Design minimizes drag, producing maximum speed in real-world rider positions - Strategically placed AeroVent ports optimize airflow through the helmet, which improves aerodynamics and adds head-cooling ventilation - AeroVent ports pull incoming air through the helmet and streams it through deep internal channels to regulate temperatures during hard efforts - TransTextura Plus anti-microbial padding helps fight bacteria growth and the natural property of the fabric inhibits microbes that cause odors - Low and high-speed impact-tuned construction with optimized low-density EPS, and an ultra-thin toughened polycarbonate shell - Element Strap System (ESS) brings together Cinch Pro, adjustable locking dividers, and LiteForm webbing into one fit and retention system for superior fit and comfort right out of the box - Integrated MIPS Cinch Pro fit system offers optimal coverage by cradling the occipital bone for full protection, support and comfort - Lightweight, LiteForm webbing wraps around the head better for a more secure fit and is hydrophobic so it won’t absorb sweat or stretch out like other webbing SPECIFICATIONS - Sizes: Western: S (51-55cm), M (55-59cm), L (59-63cm) - Weight: 230g (size M, CPSC) - Certifications: CPSC/CE, AS/NZS

The Stage Helmet: Less Weight, More Fun. Since its debut, the Stage helmet redefined mountain bike safety, style, comfort, and ventilation. The lightest full-face helmet in its class combines MIPS (Multi-directional Impact Protection System), EPP (for slow speed impacts), and EPS (for high-speed impacts) in one sleek package that sets the standard for mountain bike enduro helmets. A Polylite shell w/fiber reinforcement and Polyacrilite-injected chin bar w/EXOskeleton adds strength without sacrificing weight. 11 high-flow air intakes and 14 exhaust ports and large ventilation chin bar openings aid in cooling and comfort in all conditions. The TLD Stage Helmet also includes an X-Static helmet liner that is moisture-wicking, quick-drying, and odor-fighting. A Fidlock buckle and lightweight hardware round out this revolutionary helmet. - Polylite Shell construction with fiber reinforcement - Dual-density EPS and EPP foam offers protection against high and low-speed impacts - Featuring MIPS Brain Protection System - a helmet integrated, low friction layer designed to reduce rotational motion transferred to the brain from angled impacts to the head - Large ventilation chin bar opening and 11 high-flow intake ports and 14 exhaust vents - Contoured 3D XT2 cheek pads and washable X-Static liner create an optimized fit - Helmet includes 2-liners, 3-sets of cheekpads and 2-neck rolls for a custom fit - Innovative break-away visor screws - Fidlock magnetic buckle system - Drawstring bag with breathable mesh paneling - CPSC 1203*, CE EN1078*, ASTM F1952-DH, ASTM 2032-BMX, *Varies by regional standards

- COB LED Technology: it's a more compact footprint while delivering a higher intensity of light, meaning you'll be seen from further away and gives the lights a more uniform look - The helmet will be equipped with 98 COB LEDs in total - Front Light (30 COB LED diodes) - Rear Lights with Turn Signals (34 red COB LED diodes, 34 orange COB LED diodes) - 1100mAh rechargeable battery providing up to 10 hours with the lights set on maximum brightness - USB-C Charging Connection (Chargeable with a 5V—5.2V & 0.5A charger) - Remote included for turn Signal - Option to buy a Lumos Remote to activate Automated Brake Lights. (The Remote Lite included with Ultra doesn't come with an accelerometer and can only be used to activate turn signals) - Lumos Companion App: Customize your light flashing patterns, check your battery life, track your activity, and sync with Strava and Apple Health - Maximum Venting - MIPS technology Sizing: - Small: 51 – 55cm / 20 – 21.6" - Medium/Large: 54 – 61cm / 21.3 – 24" - X-Large: 61 – 65cm / 24 – 25.6"

The Leatt MTB Gravity 1.0 is a full-face helmet with solid protection. The focus of this helmet is premium safety and great value. Featuring 360 ° Turbine Technology, the helmet is lined with turbines which are 360 °moving discs constructed from an energy-absorbing shape and material, this tech has two exclusive advantages, namely the reduction of rotational acceleration to the head and brain and the absorption of energy upon impact at concussion level. Air vents are not covered, which makes this helmet well-ventilated. Ideal for warmer downhill or bike park days. Get full face head and brain protection at an amazing price. Details: - Downhill-certified ASTM polymer shell in three sizes - Great ventilation - 360° Turbine Technology - Reduced peak brain acceleration by up to 30% at impact speeds associated with concussion - Reduces peak brain rotational acceleration by up to 40% breakaway visor function for additional rotational impact force reduction - Double D ring chin strap - Impact foam for superior energy absorption - Washable inner liner - Optimal neck brace compatibility - Weight: From 960 ± 50g (2.12 lbs) - Certified and tested: AS/NZS 2063:2008, ASTM F1952–10, EN1078, CPSC 1203

The MET Trenta 3K Carbon Mips® is a high performance road helmet designed with elite cyclists and worn to victory at Le Tour de France and the monuments of Liège-Bastogne-Liège and Il Lombardia. Engineered to keep your head fresh and save you energy with every pedal stroke, the MET Trenta 3K Carbon Mips® is the most advanced road cycling helmet we have ever made, now upgraded with the addition of Mips AIR®, the lightest and most advanced rotational management system.

Sleek styling, cool graphics, and youth-oriented sizing make the Shuffle Child LED helmet the perfect choice for your kids—day or night. - MIPS-equipped. - Integrated LED tail light for increased visibility in in both bright and low-light conditions. - Headset SX fit system with child-oriented sizing that's designed for an easy and accurate fit. - 4th Dimension Cooling System to optimize ventilation. - In-molded shell improves strength and reduces weight. - Tri-Fix web splitter for improved comfort and ease of strap adjustments. - Reflective webbing for increased visibility in low-light conditions. - Stylish, youthful designs complement our bike graphics and colors. - Patented clip-on visor included.

Designed specifically for juniors sized youth medium. The Gambler goggle and Zoom Jr. helmet integration pack utilizes two of our most popular junior products combined for unparalleled performance and value. Gambler Goggle - Cylindrical dual thermal lens - Fog-X anti-fog inner lens - Youth fit: small - medium - Dual-slide strap adjustment system - Single-layer hypoallergenic face foam - Helmet & eyeglass compatible - Floating foam membrane eliminates eyeglass temple pressure - Silicone-backed strap Zoom Helmet - Lightweight in-mold construction - AirEvac2 ventilation - Adjustable dial fit system (DFS2) - Airflow climate control - Super-soft, furry tricot lining - Removable Goggle Lock - Youth Medium = 53 – 58cm

The MET Hooray MIPS Helmet is safe, comfortable and has plenty of toddler-specific features that will protect the next generation of cyclists. The shell of the MET Hooray MIPS has a purposely flattened part at the back in order to be comfortable in any child seat. It also covers a large part of the two most sensible brain areas; the back and the temples. The internal shape features an engineered air channeling system to facilitate airflow, while MET's unique Bimbi Secure Technology ensures that there's no pressure points on the fontanel. Thanks to the new MET Safe-T Bimbo, the helmet will grow with the child's head. The retention system is easily adjustable due to the grippy nub, and the 360° head belt ensures a stable and secure fit. The ratchet buckle makes it easy to secure the helmet and avoid unexpected pinches on the skin. - In-mold polycarbonate shell with EPS liner - Extended head coverage and integrated visor for all-round head protection - MIPS-C2 rotational management system to increase protection against certain impacts - Fontanel protection thanks to MET Bimbi Secure Technology - Anti-pinch ratchet buckle makes it easier to secure the helmet - Internal engineered air channeling system features 10 vents to improve ventilation and comfort - MET Rear LED Light, 4 Spotlights, 60h Life - Reflective rear decal to enhance visibility - Design compatible with child-seat - MET Safe-T Bimbo Fit System with 360° head belt to follow the growth of the child - Straps with adjustable dividers ensure a custom fit - Anti-insect net embedded into the front vents - Hand washable comfort pads - Intended Age: 6-8 Years of Age Sizing: - X-Small = 46 – 52cm - Small = 52 – 55cm

The Shadow Classic Helmet is constructed with a high-impact ABS hard shell with a light EPS core liner for even distribution of force upon impact. - ABS Hardshell construction with light EPS core liner - Includes two sets of padding for a custom fit - CE and CPSE certified - Shadow Crow Head rivets and Classic woven label - X-Small = 46 – 50cm - Small/Medium = 50 – 56cm - Large/X-Large = 56 – 61cm - XX-Large = 61 – 65cm

For maximum safety, the Viantor has the ActiCage structural reinforcement integrated into the EPS. It provides maximum protection while ensuring optimal ventilation and extreme comfort. - ActiCage allows for large ventilation openings without compromising the helmet's safety - Multi Shell In-Mold for durable bonding of multi-part outer shell and shock-absorbing helmet material (EPS) - Good ventilation with 4 air inlets and 14 air outlets connected with flow channels - Zoom Ace fit system with a non-slip adjustment wheel - Semi-enclosing plastic ring connected to the adjustment system for optimum stability and fit - Ponytail-compatible and well suited for braided hairstyles Sizing: - Small: 51 – 55cm - Medium: 52 – 58cm - Large: 58 – 63cm

FOR DEMANDING TRAILS The CliffHanger is the flagship trail model in the ABUS MTB series. When you're riding up and down steep hills on an enduro bike, the MTB helmet offers reliable protection. Lighter, better ventilated and with an adjustable TriVider webbing spreader—the CliffHanger scores with these features. The special MTB adjustment system also ensures that the helmet sits comfortably and firmly on the head when rattling through the wildest of rock gardens. The inner shell made of EPS hard foam is foamed into a three-part outer shell, making a lightweight and sturdy helmet. The existing Multi-directional Impact Protection System (MIPS) can reduce energy by up to 40 percent in the event of an oblique impact. With the CliffHanger, we have succeeded in developing a helmet that offers virtually perfect conditions for high speeds and demanding trails. - Multi-Shell In-Mould for a permanent bond between the outer shell and the shock-absorbing helmet material (EPS) - Zoom Ace MTB: Height-adjustable adjustment system to fit the head circumference - Ponytail compatibility: Helmet well suited for ponytail wearers - Laterally adjustable, non-slip TriVider strap system - QUIN ready—easy upgrade with the separately available QUIN chip for fall detection - MIPS: Impact protection that protects the brain, especially when the cyclist's head hits the ground at an angle during a fall. - ActiCage: Structural reinforcement integrated in the EPS to optimise stability - Moulded lower shell for added durability - Height-adjustable visor - GoggFit: Device that allows a pair of goggles to be fixed to the helmet when the athlete doesn't need them while riding - Ventilation: excellent ventilation through 8 air inlets and 6 air outlets - FidLock magnetic buckle

- 15% lighter than classic Brentwood - 20% more ventilation than classic Brentwood (13 vents) - Zip Mold + construction - EZ-Fit retention system - Compatible with Bern Asteroid light - Removable flip visor - Average weight: 345g - MIPS: multi-directional Impact Protection System

- Visor: Yes - Impact Protection System: MIPS - Certification: CPSC, EN1078 - e-Bike approved: No

The MET Trenta MIPS a performance road helmet engineered to maximize ventilation and save you energy with every pedal stroke. Featuring the MIPS-C2 rotational management system, the MET Trenta MIPS is able to slide in the case of a crash, redirecting damaging rotational motion. MIPS is a brain protection system—engineered to add protection to the standard construction of helmets in case of certain impacts. Scientifically designed air vents harness the power of the Venturi effect, pushing out warm air within the helmet through specially positioned exhausts to ensure constant airflow. The tail of the helmet also features an aerodynamic design to effectively drive airflow. - In-mold polycarbonate shell with EPS liner - MIPS C2 rotational management system is engineered to add protection in case of certain impacts - Exceptionally comfortable and secure on the head thanks to refined internal shape - MET Safe-T Orbital Fit System - 360° head belt, and vertical and occipital adjustments offer a customized fit - Air Lite straps with adjustable divider maximize aerodynamic and comfort - 19 vents and an internal air channeling system are engineered to improve ventilation and comfort - Sunglass ports securely dock sunglasses when climbing or resting - Tube-shaped tail improves aerodynamics - Limited contact with the surface of the head helps to maximize the ventilation - Certifications CE; AS/NZS; US Sizing: - Small = 52 – 56cm - Medium = 56 – 58cm - Large = 58 – 61cm

A HELMET MADE FOR THE CITY STREETS The Pedelec 2.0 is an uncompromising combination of protection and comfort. Complemented by clever features, it is the ideal companion in road traffic. In big city traffic, a helmet is an indispensable companion for you as a cyclist. Accidents happen quickly and if you fall, a bicycle helmet protects you against serious injury. With the Pedelec 2.0, ABUS offers a bicycle helmet that meets the high safety requirements of the big city. Its deep temple area provides the required additional protection. The Pedelec 2.0 is also characterised by the integrated rain hood, which can be quickly pulled over the helmet at the first sign of rain. The especially bright, rechargeable light and the replaceable visor offer additional, passive protection. - This NTA 8776 helmet is a helmet that complies with the requirements in the Dutch Technical Agreement (NTA) 8776. - In-Mold for a durable connection with the outer shell with shock-absorbing helmet material (EPS) - High visibility due to powerful reflectors - Large, highly mounted and integrated LED tail light with 180° visibility - Forced Air Cooling Technology: Sophisticated ventilation system for an optimal head climate - Excellent ventilation with 4 air inlets and 9 air outlets connected with flow channels - Ponytail compatibility: Helmet well suited to plait wearers - Zoom Ace Urban: Finely adjustable adjustment system with handy adjustment wheel for customisable fit - Size adjustment by means of a half ring made from particularly hard-wearing and slightly malleable plastic for optimal stability and form fitting - Foamed-in fly nets - Lower edge protection: Provides the helmet with additional protection from external influences - Fidlock magnetic strap buckle - Rain cover integrated in the helmet