The GameBreaker Stealth Helmet Liner is a helmet insert fully powered by an innovative smart molecule technology. D3O(R) materials flow freely when at rest, but on impact, lock tightly together to disperse and absorb the energy of the blow, before instantly returning to their soft, flexible state. This reaction is instantaneous and 100% passive. The greater the force of impact, the greater the protection. The helmet padding insert liner has the ability to reduce the SI (severity index) while fitting comfortably inside all helmets, caps, or beanies. PERFORMANCE TECHNOLOGIES: Protected By D3O Full Head Coverage One Size Fits All Ventilated for Max Air Flow ADDITIONAL SPECS: NO METAL OR HARD PLASTIC COMPONENT PARTS