The Snell website has a list of all helmets certified to their current M2015 impact standard. There’s only six brands with current motocross models:
Arai: VX-Pro4
Bell: Moto-9 MIPS, Moto-9 Carbon Flex, Moto-9 Custom-Fit
Fly: F2 Carbon MIPS
HJC: CL-X7
Shoei: VFX-EVO
Troy Lee Designs: SE4 Carbon MIPS
Including old models back to 2015, there’s another 13 models from 11 brands:
Arai: V-Cross4
Bell: Moto-9
EVS: Vortek-T7
Fly: Formula
FXR: FX-3
Helmet Solutions: HMX-F1 (FXR)
HJC: CL-X6
LS2: MX456
O’Neal: 9 Series, 7 Series
Shoei: VFX-W
Troy Lee Designs: SE3 Carbon, Air
Plus these six current snowmobile helmets:
FXR: Blade
HJC: FG-MX, FG-X
Polaris: Demon 2.0
Ski-Doo (BRP): XP-3, XC-4
The Snell website has more information about their M2015 standard, comparisons to other standards, their test methods, and the science behind it. The Bicycle Helmet Safety Institute has useful information about various test standards and what they mean in terms of speeds, concussions, brain injuries, etc. at helmets.org.
Also noteworthy: Leatt publishes independent impact test reports and 6D has some test information on their website that addresses concussions and traumatic brain injuries. But until the medical community can agree on performance parameters that prevent concussions/traumatic brain injuries, there won’t be certification test standards that address this. Current motorsport helmet certifications only evaluate brain accelerations with the goal of preventing death.
I hope consumers consider the impact performance data when deciding which helmet to wear.