When choosing a mask, fit and field of vision come first. The M-4 gives you the best of both worlds, fitting a wide variety of faces and offering superior peripheral and vertical vision. It is low profile, stows easy and carries an excellent value. Mask has a single lens made from tempered glass for excellent optical characteristics and safety. The frameless black silicone skirt has a double feathered edge for a perfect seal, large one handed nose pocket for easy ear equalization. The easy adjust-buckles and quality wide split black silicone mask strap will keep the mask properly in place for even the longest day of diving, and when the day is over stow your M4 in the accompanying mask box.