4 In. Round Infrared Window, Maximum Operating Temperature Degrees F 450 Degrees F, Minimum Operating Temperature Degrees F -40 Degrees F, Optic Maximum Temperature 2, 552 Degrees F, Viewing Aperture Area 9.79 sq in, Viewing Aperture Diameter 3.5 in, Viewing Aperture Height Not Applicable, Viewing Aperture Width Not Applicable, Window Thickness 0.16 in, Body Maximum Temperature 1, 219 Degrees F, Includes 4 in (100 mm) C-Range IR Window, Kwik Twist, IP Rating IP65. This item has been restricted from sale in the following state (s): []