Unique 4-corner thread form with raised ridge reduces driving torque penetrating the hardest wood products. 6-lobe drive virtually eliminates driver bit cam-out. Self-countersinking nibs under head insure flush installation. Penetrate hardest wood products with ease, often without pre-drilling. Made of solid 316 stainless steel for maximum corrosion resistance. Threaded approximately 2/3 up shank to tightly draw deck board to joist. NOTE: Contractor"s Packs containing 1750 screws will fasten 500 square feet of decking. Deck Packs containing 350 screws will fasten 100 square feet of decking (6" boards on 16" centers). 6-Lobe Driver Bit included in both Contractor and Deck Packs. Drive flush with surface of workpiece.