When you learned how to dive your instructor told you the most important part of choosing equipment was comfort and fit. When looking for a mask you also need a great field of vision well this mask was designed to meet those and more desirable qualities. The Sub-Frame Two-Windowed Mask is a low volume mask which offers you a wide field of vision and because of its frame design is one of the most durable masks found on the market today. This durability has been achieved with a Sub-Frame that is molded and bonded directly to the mask's silicone rubber skirt. A second frame made of corrosion resistant 316-grade stainless steel protects the nose bridge area and adds strength and ultimate durability. Mask has optical quality glass lenses and squeeze-to-adjust buckles.