This is designed to thread into the wall fitting using the 1-1/2\" male threads on the front. The opposite side is designed to fit a 1-1/2\" inside diameter pool filter hose.. (1-1/2\" male threads actually measure about 1-7/8\" diameter\") Thread diameter : 1-7/8\" (1-1/2\" MPT) Length: 3-3/8\" Smooth end diameter: 1-1/2\" \"SP-1091-Z-4\" is molded on the side