The Atomic Aquatics SubFrame Medium Fit Dive Mask is built with UltraClear technology, a two window design, and an innovative three piece frame structure. The Atomic Aquatics Ultra Clear Sub Frame Medium Fit mask is a two window design built with an innovative three piece frame structure, allowing a lightweight design with a structure that provides unparalleled comfort, durability, and strength. The medium fit mask has a skirt designed for narrow faces, but is identical to the standard model in every other detail. Features: Silicone rubber skirt molded directly around the sub-frame for extra comfort Two window design with incredible strength, comfort, and rigidity Distortion-free UltraClear removable lenses Lifetime warranty against frame breakage A great fit to complete the combination of function, style, and durability