The shell is smoothly finished material that provides the general outer form the helmet. It protects the head from direct impact and penetration from flying or falling objects.
Holes inside the shell fix the harness in place.
The Fitting suspension are composed of a hammock, a headband, a chinstrap etc. These fittings are the parts other than the shock absorbing liner, which are fitted to the inside of the shell in order to soften the impact acting on the head of the wearer.