Box of 11. Use to seal unused opening on a catch basin drain to direct water toward opening with connected drain pipe. Works with 9 in., 12 in., 18 in., & 24 in. catch basin drains. Outlet plug securely seals the catch basin opening—no tape or glue required. Made to fit keyed opening in catch basin and locks in place. The outlet plug seals unused opening of catch basin; unsealed catch basin opening(s) connects to drain pipe; as part of a complete drainage system, water is captured and directed away for proper release downstream. Insert outlet plug into keyed catch basin openings to lock in place. Fits 9 in. 12 in. 18 in. 24 in. Catch basin openings