... while allowing the light to pass. The material of windows must be considered first, for different material with different ... be considered with certain environment.We supply large of windows with different materials, including BK7 glass, other specific ... glass, Fused Silica, Sapphire, CaF2, etc..BK7 Windows High Precision BK7 WindowsStandard BK7 WindowsSpecifications:Material: BK7 grade A ...