Spax Hex Washer Head construction fasteners with HCR coating are intended for wood-to-wood connections in exterior structural applications when attaching treated lumber components. These fasteners are designed with a hex-head conventional driver system along with a built-in washer for applications requiring additional surface area under the head for superior pull-down force. Often used for blind, high-torque applications where you need additional engagement from a socket to a screw head. Cold-rolled carbon steel wire heat treated to Grade 5 durability and plated with an HCR (High Corrosion Resistance) double barrier coating. "HCR" is tested and recognized for use in ground contact pressure treated lumber for exterior, freshwater general construction applications.