The Valterra RV Freshwater Inlet is a standard city water inlet. It's made with a durable plastic flange and brass fitting so it won't rust. It has a garden hose swivel fitting with gripper and press-in dust plug. It has an integrated check valve for back flow prevention. The flange has a diameter of 4-3/4".SpecsOutlet: 1/2" FPTCity Inlet: 3/4"Cutout Dimensions: 3-1/2" dia. Outside Dimensions: 4-3/4"Valve Depth: 2-1/2"Flange Material: White Plastic Durable plastic flange & brass fitting so it won't rust Swivel fitting with gripper & press-in dust plug Integrated check valve for back flow prevention | Valterra A01-0176LF RV Freshwater Inlet, Recessed Flange, 1/2" FPT, White