Sioux Chief 3" Hub/Inside 4" Schedule 40 DWV PVC Closet Flange a total knockout design that sits flush to the floor, ensuring the closet flange will not break apart or fall down the drain pipe. This innovative design makes installation easier by eliminating the need to hold the knockout while hammering. It can hold 5 feet of water (22 P.S.I.) for head testing, providing reliable performance. The inside diameter of the pipe can vary significantly, but these flanges are designed to fit inside most types of pipe, although they may not fit all. Model Number: