The most important consideration in mask selection is ?t. No two faces are alike, so SCUBAPRO's broad range takes individual differences into account. One basic difference in masks lies in the number of lenses. SINGLE-LENS masks remain a popular choice worldwide because they provide a broad, uninterrupted view. TWIN-LENS masks have become increasingly popular because they typically lower internal volume and are easier to clear. To increase peripheral vision and transfer more light, SCUBAPRO has incorporated side lenses into selected masks. A ?nal consideration in mask selection is ease of clearing. Low-volume masks and models with purge valves make clearing easier, even for the less experienced diver.