Ace Race Parts 23713 Oil Drain Flange 1/2 FNPT with O-Ring Style Seating Surface (2.000 Bolt Circle)Ace Race Parts 23713 Oil Drain Flange 1 2" FNPT with O Ring Style Seating Surface (2. 000" Bolt Circle) The Ace Race Parts brand of Oil Drain Flanges are offered in a wide range of configurations. This particular Oil Drain Flange features an integrated 1 2" Female NPT Thread Outlet and an O Ring Style Seating Surface to ensure a leak free connection at all times. Ace Race Parts oil drain flanges are precision CNC machined from solid 6061 T6 Aluminum