Wej-It Wej-Con Concrete Screw, 1022 Carbon Steel, Blue R-Blocker Finish, Hex Washer Head, Slotted Drive, Fits 1/4" Hole Size, 1-1/4" Length, 1/4" Threads (Pack of 100) Concrete screw cuts threads into concrete, hollow block, brick, mortar, and concrete masonry units to provide a secure hold without requiring threaded inserts 1022 carbon steel screw has a corrosion-resistant blue R-Blocker coating that meets ASTM B117 specifications to resist 1,000 hours of salt spray Hex washer head has a flange that provides additional bearing surface to distribute the force over the fixture being fastened and has a slotted drive for use with a flat-blade driver Ultimate tensile strength is 670 lb. at 1" embedment depth and 1" edge distance in 2,730-psi concrete Use one-fourth or less of listed maximum values for safe working loads (as required by local regulations)