RX Scuba Dive Snorkeling Purge Mask Prescription Lenses Farsightedness/Nearsightedness/Plain Promate Pro Scanner Scuba Dive Purge Mask (Rx-Able)/MK650: Nearsight Optical correction lenses available from -1.0 to -10.0 by increments of 0.5. Farsight Optical correction lenses available from +1.0 to +4.0 by increments of 0.5. Bifocal Optical correction lenses, also called Gauge Reader available in +1.0, +1.5, +1.75, +2.0, +2.25, +2.5, +2.75, +3.0, +3.5, +4.0. Underwater Mirror Coated color correction lenses is also available in Red ,which brings up lost red color at depth - great for warm water diving and Yellow, which for increased light, higher contrast and better separation, especially in low visibility.