(m) Retention system is the complete assembly that secures the helmet in a stable position on the wearer's head. (n) Shield means optional equipment for helmets that is used in place of goggles to protect the eyes.

Retention system: Some brands refer to their retention system as a ratchet system used to tighten an inner shell, but in this case, we are referring to the retention system underneath the chin. When properly tightened you should be able to fit two fingers between the strap and your chin and the strap should make a V shape underneath your ears.

A helmet including a retention mechanism comprises a shell for protecting a head of a person and a fit system elastically coupled to the shell. The fit system comprises a bowl designed to fit an occipital region of the person's head and a hinge for coupling the fit system to the shell, the hinge permitting the fit system to move.