TUSA Freedom Film Anti-Fog Sheets for 2-Window Dive Mask, Clear will keep yourfavorite mask fog-free while diving or snorkeling. Made of a long-lasting,clear, durable urethane, the Freedom Film can be installed easily on any twowindow mask and is reusable with proper care. Installation is a simple, threestep process. First, gently apply the film to the center of the lens. Next,while holding down the film with one index fingertip, repeatedly slide theother index fingertip from the narrow end of the film outwards, pressing outany air bubbles. When all air bubbles have been eliminated, youre ready todive. (Full instructions included inside package)