A helmet including an insert provides the ability of including a highly energy absorbing feature within the insert. The insert includes a structure such as a Bingham plastic which, upon impact, absorbs the energy of the impact by converting from a solid to a liquid. Other energy absorbing features are contemplated. The energy absorption process occurs in one aspect in a nonreversible manner such that once a high enough level impact occurs on the insert, it must be replaced within the helmet. The insert has a fastener which enables it to be replaceable. In this manner, a highly absorbing feature of a helmet can be provided to reduce concussions while not requiring the complete replacement of a helmet.