Borofloat and Pyrex are borosilicate glass. Borosilicate glasses are known for having very low coefficients of thermal expansion (~3.3 × 10-6/°C at 20°C), making them resistant to thermal shock, more so than any other common glass. Windows made of Borofloat and Pyrex glass are less subject to thermal stress than BK7 windows.
Note for Borofloat windows:
1. Custom-made Borofloat windows at any size from 2.0mm to 200mm clear aperture are available. besides round, Borofloat windows at shape of quadrate ,triangular or other polygonal are available
2. Thickness from 0.5mm to 30.0 mm is available upon request.
3. Better bevel is available upon request.