The M-17"s 1-window design offers exceptional visibility, low-volume and enhanced comfort while incorporating our patented 3-D Strap and Round Edge skirt technologies. A newly designed skirt mounted Quick-Adjust Buckle System further enhances comfort and ease of fit. TUSA"s patented 3-D strap is a true three-dimensional design that snugly fits against the head"s natural curvature. The 3-D strap offers unprecedented comfort and fit unlike standard flat mask straps. The 5 Angle Strap Adjustor allows for a five-position micro-adjustment on both the left and right sides of the mask. This enables vertical (up/down) and horizontal (left/right) pressure on the face to be delicately adjusted for the optimum fit. TUSA"s Round Edge Skirt features a proprietary round edge cross-sectional shaped skirt. This rounded edge results in a soft fit that suppresses pressure and reduces creasing left on the face. The "planar fit, instead of linear fit" silicone skirt maintains great fit and unprecedented comfort. Additionally, the Concero is the only 2 color frameless mask available on the market today. You also get a Free Save-A-Dive Kit with your mask.