This is the ScubaPro Prescription RX Lens for Twin Mask Zoom Evo Mask - Optical Lens Features: Scubapro Flux Twin Corrective Lens Please note there will be an additional 2 to 3 days processing time for most RX lenses Fits: Scubapro Flux Twin Mask (See SKU: MSK359) Cost is per single lens only Improves Underwater Vision Easy to Install -1.0 to -8.0 Diopters -0.5 Increments Increased Diving Safety Tempered Safety Lenses See Instruments Better Must for Photographers Just as eyeglasses are the easiest and safest way to correct vision topside, corrective lenses are the simplest and most cost-effective choice for correcting it underwater. 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 Diopter lenses for your dive mask. Returns are not accepted for used lens. Only unused lens are eligible for return with store credit.