These are Optical Windows made of Fused Silica Material. In additional to excellent transmission in the UV to NIR regions, fused silica windows exhibit more shock resistance, lower thermal expansion, higher laser damage threshold and better chemical homogeneity.
Ross Optical Industries
Fused Silica Precision Window
6 mm (0.2362 inch)
60-40 Scratch / Dig
Window Diameter, Side Length, or Rectangular Length