Optical WindowsOptical windows are used for protecting fragile optical components inside an assembly. Substrate material is BK7, B270, Float Glass, Borosilicate, or UV Fused Silica. Specification: Material: BK7, UVFS, quartz, float glassDiameter: +0.0/-0.2Thickness: +/-0.1Parallelism: 1"Wavefront distortion: 1~5Surface Quality: 40/20Coating: Optional