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 diving you need to get a set of Negative DIOPTER lenses for your dive mask. See things clear underwater with this Oceanic Negative DIOPTERS for your Oceanic Ion Mask. Easy to install and WOW! You can now see everything better than before. Lenses are made of Tempered Glass and are available from -1.5 to -8.0 in -0.5 increments for Left-or-Right Side Lens. Lenses are covered by a 12 month limited warranty.