Dryer power outlet that accepts aluminum or copper conductors. Designed to be installed in 2-gang electrical boxes without mud rings. Maximum 4 AWG (American wire gauge). 3-pole, 3-wire, non-grounding. 2.15 inch diameter. 30 amp/125 volt/250 volt. Black, NEMA (National Electrical Manufacturer's Association) 10-30R. UL (Underwriter's Laboratories) listed.