It should have a thick padding of thermocole- at least 20 mm- which must extend to the sides of the head. A full face helmet is safer by all means.
This is a molding of polystyrene beads or polyurethane foam. It provides a stopping distance for the head. The foam can compress by 90% during an impact, although it recovers partially afterwards. But this helps increase the stopping distance thus reducing the peak deceleration of the head. It also protects as much as possible of the head.
It is essential to wear a well-fitting helmet for the effective working of chinstrap system. To test if the helmet fits your head properly, tightly fasten the chinstrap and then pull helmet off forward by gripping the rear and then pulling. The strap must be threaded correctly so that the buckle locks the strap when it is pulled from the chin side. The strap must be pulled as tight as is bearable under the chin.
