GMax · AT-21S
GMax AT-21S
Quick Facts at a Glance
Verified Safety Snapshot
How this helmet’s verified certifications map to recognized safety homologations and crash testing.
Safety standards compliance is based on official manufacturer documentation and public safety laboratory test results. Always verify regional compliance labels on the physical helmet prior to use.
Verified Fit & Sizing Guide
Head shape profile matching and interactive size calculator based on verified manufacturer dimensions.
How to measure
Wrap a cloth measuring tape around your head just above your eyebrows and ears. Pull the tape comfortably snug, read the length, and repeat for consistency.
Design Concept & Background
"Built for Speed"
The GMax AT-21S is engineered for the versatile rider who demands performance both on the pavement and off the beaten path. Combining sleek, modern styling with advanced aerodynamic shell geometry, this helmet minimizes wind buffeting at higher speeds while maintaining a lightweight profile that reduces neck fatigue during long-distance adventures. The advanced channeling ventilation system is strategically designed to optimize airflow, effectively regulating internal temperature and preventing visor fogging in varying climate conditions. Vision is prioritized through an optically correct, wide-port face shield that offers superior peripheral awareness, ensuring you stay focused on the trail ahead. Built with a durable polycarbonate shell, the AT-21S provides robust impact protection without compromising on comfort. The interior features a plush, moisture-wicking liner that is fully removable and washable, complemented by adjustable cheek pads to ensure a personalized, secure fit. Whether you are navigating technical dual-sport terrain or commuting through urban environments, the GMax AT-21S delivers the perfect balance of safety, comfort, and functional versatility for the modern adventure enthusiast.
Key Highlights:
Rider Profile & Intended Use
Where to buy
| Retailer | Price | Availability | |
|---|---|---|---|
| Amazon (US) | Check live price | View on site | Check Price → |
Price History & Trends
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Product Concept & Specifications
GMax (United States)Engineering & Biomechanical Safety Analysis
The GMax AT-21S features a polycarbonate shell, providing excellent impact protection and durability. It offers a comfortable fit with adjustable cheek pads and a ventilation system that helps regulate temperature and reduce fogging.
The GMax AT-21S is engineered as a high-integrity Adventure/Dual Sport protective system, utilizing a structural shell constructed from Polycarbonate. This structural layup is engineered to provide progressive kinetic energy dissipation during impact deceleration, distributing localized shock across outer lamina layers while minimizing deformation transfer into the internal multi-density EPS liner.
Certified to DOT, ECE 22.06 protocols, the architecture is subjected to rigorous linear deceleration limits and oblique impact evaluations to mitigate rotational acceleration forces associated with diffuse axonal injury. For a deeper breakdown of rotational thresholds and impact testing speeds, consult our ECE 22.06 vs DOT vs SNELL engineering benchmark.
Internal geometry follows a Intermediate Oval cranial profile, designed to mitigate focal pressure hot spots across the parietal ridges while maintaining uniform radial clamping pressure along the zygomatic arch. Riders seeking optimal retention stability and break-in guidance should review the cranial aspect ratios and head shape guide as well as our 3D cheek pad density protocol.
Shell composite integrity and acoustic sealing are further optimized through channelized EPS porting and aerodynamic laminar profiling. To learn how shell composites resist stress cracking under prolonged environmental cycling, inspect the composite material comparative matrix.
Fit & Shell Structure
Intermediate Oval Shape
Balanced oval fit: standard ergonomic curvature fitting 80%+ of riders.
Safety & Certifications
Acoustics & Aerodynamics
Technology & Convenience
Interactive Size & Fit Finder
How to measure
Wrap a cloth measuring tape around your head just above your eyebrows and ears. Pull the tape comfortably snug, read the length, and repeat for consistency.
Part numbers
| Product style | MFR. product # | SKU | Availability |
|---|---|---|---|
| Gloss Black / | — |
GMA-AT21-BLK | instock |
| Anthracite / | — |
GMA-AT21-GRE | instock |
| Hi-Viz Yellow / | — |
GMA-AT21-YEL | instock |
| Urban TC-1 / | — |
GMA-AT21-URB | instock |
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Compatible Motorcycles for the GMax AT-21S
Calibrated for upright windscreen deflection, all-terrain dust filtration, and long-travel suspension dynamics.
Data Confidence & Verification Provenance
Helmetsan enforces field-level verification and multi-source cross-referencing. Unverified values are explicitly flagged rather than estimated.