Window Material: impact-resistant Polycarbonate, Black Plastic & Rubber Sealing Door thickness: 48-52 mm (1.89" - 2.04") Diameter for circular placement of mounting holes: 195 mm (7.78") Circular inspection window in transparent, impact-resistant polycarbonate Intended for HVAC-applications using insulated doors Mounting uses 6 pcs M6 x 60 mm stainless bolts Nuts and bolts are included with the product