Abstract: A protective helmet and method and apparatus for making same. The helmet is made of an expanded, resilient polymer and configured with an undercut portion and with holes for ventilation and/or the mounting of a helmet retention system. The holes are generally perpendicular to the surface of the helmet at the hole. The mold for making the helmet includes a core and a cavity. The cavity is configured with projections for molding holes in the back of the helmet and the core is configured with projections for molding holes in the front of the helmet. The space between the core and cavity when in an engaged position defines the shape of the helmet, including any desired undercut portions. The helmet is molded by injecting compressed, resilient polymeric beads into the mold, venting the mold while applying heat to expand the beads, permitting the mold to cool and retracting the cavity from the core along a line of retraction to release the part from the mold.