This is the Bare Sport Frameless Scuba Diving Mask Features: Low volume frameless mask with single lens Revolutionary push-button buckle allows for easy, quick strap adjustment Unique flexible buckle attachment swivels with facial movements and absorbs shock, preventing buckle breakage when mask is bumped Ultra clear tempered glass lenses Low volume double-flanged black silicone skirt Sport Frameless is a low-volume single lens design that incorporates a soft, supple double-flanged silicone skirt for an excellent face seal.