Lego minifig compatible Custom SI-Dan Toys HGU-56 Helmet, fits on a minifigures head and can be used with the SI-Dan toys Gas masks (if you don't use the helmets face guard). It also has a rail to clip ANVIS-S2, ANVIS 9, SD21, SD23 and PVS14 Night Vision Goggles and TA02  & X500 Goggles - Not included, all sold separately.