The M-1 Mask sets new standards for optical quality and distortion-free vision, making it the most critical part of each dive. The lens is made of an extremely transparent glass that is prized for its appealing appearance and optical properties for divers. Because of the low iron content, the glass transmits more light and has less of the green tint that other glasses have. This eliminates lens distortion and improves color and visibility underwater in low-light situations when snorkeling.