Hydrotac lenses turn any eyewear into bifocal reading glasses with superior clarity! Lenses are easy to install and position— they are removable and reusable with no residue left behind. Provides optically correct magnification on any eyewear. Hydrotac lenses are lightweight, ultra-thin pliable lenses. Can be trimmed to size with a sharp scissor, and positioned anywhere on the lens. Includes protective case to keep them safe when not in use. Polymer aspheric material.