Bicycle helmets by absorbing the impact of the crash to be effective. In short, the inside of the helmet bubble inner cushion the impact of the impact of your skull. Traditionally, many bicycle helmets are composed of EPS foam (polystyrene) foam materials. Once the deformation of EPS foam pieces in the accident, so it will not restore and no longer have the ability to absorb collision impact. EPP foam (pp) foam can be restored after the hit, but the ability to absorb the impact is far inferior to EPS foam. Gm GeCet is also a kind of widely used in bicycle helmet bubble material, it is actually a stronger EPS foam type, more is not easy to crack.