Heater, exhaust fan and light combination. Installs in ceiling. Heater blower wheel is one piece metal and electronically balanced. Ventilation blower wheel is one piece polymeric and electronically balanced. Ultra safe ceramic heating element bonded to large heat transfer surface allows heating at very low operating temperature. Self regulating design provides 1,350 watts. Moonstone glass lens, installed in a flip down lens holder. 100 watt incandescent capacity, type A lamp required, bulb not included.UL listed. HVI2100 certified. Duct Collar: 4 in round, zinc plated metal collar adapter with aluminum back draft damper.