Helmet

A helmet comprising: inner and outer shells configured to slide relative to each other; and a connector connecting the inner and outer shells so as to allow the inner and the outer shells to slide relative to each other, the connector comprising: an attachment part attached to one of the inner shell and the outer shell; wherein: the attachment part comprises one or more protrusions and the inner or outer shell attached to the attachment part comprises one or more channels into which the protrusions extend, the protrusions and channels are configured such that the protrusions can move within the channels in an extension direction of the protrusions, during sliding of the inner and outer shells relative to each other, and the protrusions comprise an abutment member configured to abut an abutment portion of the channel to prevent the protrusion leaving the channel.