They are UL-844 and C-UL/CSA C22.2 No 137 listed for hazardous locations. The illumination port with a standard sight glass lets video or TV cameras be used while the light is on. Attached brackets let the fixtures easily mount on existing pressure vessels. Lights are made from corrosion-resistant, thick-walled castings and all metal joints are either threaded or ground. The lens is a finely ground borosilicate glass.