The Valterra RV Freshwater Inlet is a standard city water inlet. It's made with a durable plastic flange and fitting so it won't rust. It has a garden hose swivel fitting with gripper and press-in dust plug and an integrated check valve for back flow prevention. The flange has a diameter of 2-3/4".SpecsFlush MountInside Connection: 1/2" MPTFlange: 2-3/4"Cutout: 1-1/4" Garden hose swivel fitting with gripper Press-in dust plug Integrated check valve for back flow prevention | Valterra A01-0168BK RV Freshwater Inlet, 2-3/4" Flange, 1/2" MPT, Black