usa Freedom Quad Dive Mask features the newly developed and revolutionary Freedom Technology delivering superior fit, comfort and performance. The Freedom Quad fit line, lens and frame shape are derived from the popular Freedom One with added features of CrystalView Glass and Panoramic View. The skirt is also one of the best we have seen: Thanks to the varied silicone thickness it is extremely thin where it needs to be but still robust enough to hold the shape. This feature allows the mask to provide a superior seal and fit while minimising leakage. Facial characteristics and shape are unique to every person and traditional masks can therefore cause discomfort underwater. TUSA engineers solved this problem after years of analysing mask fit, facial bone structure and mouth movement. The result is a set of revolutionary new mask features delivering superior fit, comfort and increased performance. Please note that the lenses in the TUSA Freedom Quad cannot be changed for prescription lenses. Freedom Freedom technology is a set of revolutionary features offering superior fit, comfort and increased performance in TUSA masks. Freedom model masks feature a dimpled skirt surface with varied silicone thicknesses and stability ridges in addition to a proprietary low-friction skirt surface on the fitting line. TUSA 3D Mask Strap 3-D Strap 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. TUSA CrystalView Optical Glass CrystalView Optical Glass CrystalView optical glass lenses provide superior clarity, colour and transmission of light over standard glass lenses used by the competition. Up to 15% of available light can be lost with a standard glass lens due to impurities and reflectivity. TUSA's CrystalView lenses transmit 92% of available light to the diver for clear crisp vision. CrystalView lenses are used in all PRO models masks and also in the M-41 Freedom Quad. TUSA Panoramic View Panoramic View Panoramic View masks feature a variety of designs offering an incredibly wide field-of-view. Several designs incorporate minimum frame volumes, domed side-windows, reduced frame structures as well as three and four window styles for maximum vision. TUSA Round Edge Skirt Round Edge Skirt TUSA's Round Edge Skirt features a proprietary round edge cross-sectionally 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. TUSA Quick Adjust Buckle System Quick-Adjust Buckle System The Quick-Adjust Buckle System incorporates a newly-designed low-profile buckle. The result is a compact, lightweight, technologically advanced mask design that can be easily and quickly adjusted for a perfect fit.