This is the Wide-i Magnetic Underwater Fog Wiper for Scuba Diving Masks - One Magnet set for Single Lens Mask Features: Requires no training Conserves Air (by preserving air used on rinsing mask) Clears view when desired Keeps cold or contaminated water away from face (by not rinsing) Chemical free (will not irritate eyes) Does not wash off like anti-fog solutions Everlasting (never runs out") Optimal for scuba diving and snorkeling masks, it also fits safety goggles. It works on prescription lens masks, with powers as high as +/- 10 diopter. It can be used on airsoft/paintball masks, too, as long as one is not wearing gloves (because these are too small to be grabbed/moved with gloves). Note that ONE unit (quantity=1) of this product is needed for single lens masks and TWO units (quantity = 2) are needed for dual/split lens masks