OPTX 20/20 Reading Lenses adhere to the inside of your glasses by static cling adhesion. They are removable and reusable. No glues or adhesive are necessary. OPTX 20/20 lenses easily install with water. OPTX 20/20 adds optically correct magnification to sunglasses, safety glasses, and prescription eyewear. The lenses turn your favorite glasses into bifocals simply with a drop of water. No more squinting. No more stacking reading glasses with sunglasses. OPTX 20/20 can be trimmed to fit any glasses. Turn you favorite pair of sunglasses into bifocal readers without the expense of custom prescription lenses. 2.50 Diopter.