Sight window with threads conforming to ASME B1.20.1. Sapphire window is hermetically sealed into the housing with a Aflas® seal. For visual inspection, machine vision, laser sensors, in use with all common hydraulic oils, refrigerants, pharmaceutical processing equipment. This sight glass is an ideal choice for applications requiring no compromises in optical clarity. The window is flat on both sides, and precisely polished to surface quality of 50-25 S-D per MIL-O-13830. Because the window material is C-Axis sapphire, this sight glass can be used in applications requiring extended transmission ranges. Specifically, this window transmits over 50 percent of light in the range 200 nm - 5.0 µm wavelength. The window is sealed into the housing with a high durometer Aflas seal. This sight glass has a long working life under severe temperature swings and prolonged exposures to UV light.