The Atomic Aquatics SubFrame Mask is so durable; it carries a Lifetime warranty against frame breakage. The strength comes from the internat frame (Sub Frame) molded directly beneath the surface of the silicone rubber skirt. The subframe provides incredible strength and rigidity as well as eliminating the bulky external plastic frame in other masks. A stainless steel retainer locks the lenses in place and provides additional strength to the nose bridge area of the mask. A wide field of view and great fit complete the combination of function, style and durability. All SubFrame masks are available in a medium fit for narrower faced except for the SubFrame ARC Technology.