1. The types of helmets, which are mainly divided into:full face helmet,  off-road helmet , open face helmet and  flip up helmet.
2 when wearing the helmet, you should clearly hear and distinguish the sound from all directions, and there should be no vibration and other noise when driving.
3. The inside of the helmet should have good ventilation and warmth device, and should be dust-proof, insect-proof and waterproof.
4 helmet should have good reflective and thermal radiation resistance.