Hollis M1 MaskThe M1 Mask raises the bar for optical quality and distortion free vision. The lens is made from a highly transparent extra clear glass which is valued for its unique appearance and optical qualities. The low iron oxide content gives it optimum clarity. Its light transmittance is greater than that of conventional glass. The use of UltraClear glass results in a virtually colorless product which allows objects to remain vivid and natural. This makes the