The freedom One Pro Mask uses CrystalView Optical Glass. These lenses provide superior clarity, color 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. TUSAs CrystalView lenses transmit 92% of available light to the diver for clear crisp vision. CrystalView lenses are used in all PRO models masks.