Composi-Lok screws eliminate mushrooming in composite deck lumber. Multi-layer coating prevents bleeding and staining. Designed for use in Trex , Timbertech , Certainteed Boardwalk , and Everx . For use with Quik Drive fastening system. 2-1/2", square drive, No. 2 square undersize recess. Quik Guard coating can be used with any and all pressure-treated lumber.