The low profile and close fitting STARLIGHT adjusts easily via a simple twist knob at nape of neck - great for adding or subtracting a balacava or ball cap (make sure to remove the "button" at the top of your cap - before using under a helmet). The STARLIGHTS impact absorption is provided by resilient and crushable foam layers of high density polystyrene co-molded to the polycarbonate shell's interior. Plush lined push button chin strap and head cradle plus high tech vents keep you cool and comfortable.