4 In. Round Infrared Window, Crystal Insert Size 100mm dia, Viewing Aperture Size 89mm dia, Viewing Aperture Area 6322 sq mm, Window Thickness 4 mm, NEMA Rating 12, 3, IP Rating 65, Gasket Maximum Temperature 250 Degrees C (482 Degrees F), Body Maximum Temperature 659 Degrees C (1219 Degrees F), Optic Maximum Temperature 1400 Degrees C (2552 Degrees F), Voltage Range Any, Components Grounder Metal, Body Material Aluminum, Includes Access Key and Installation Instructions on a CD