Tired of not being able to see well underwater? Can't read your computer or gauges? Maybe you not sure what F-Stop you are setting your camera on? If these are problems for you when you are diving you need to get a set of negative diopter for your XS Scuba M-Line, MRx Mask and these lenses fit many of today's most popular masks. The diopter covers entire surface of lens for excellent corrected underwater vision. Easy to install on masks these lenses are made from the highest quality optical glass, precision ground and polished tempered glass. The lenses meet ANSI Z86.11.1985 standards and are available in -1.0 to -8.0 negative diopters in -0.5 increments. Lenses are covered by a 24 month limited warranty.