GRK R4 Stainless Steel self-countersinking screw has a new underhead with saw-blade like cutting teeth and six self-contained cutting pockets. Together they act similar to a circular saw-blade, transporting the drill dust away from the edge of the screw hole while cutting a perfectly clean hole into even the most brittle materials without cracking any surface treatment. This design also further enhances the R4’s versatility by allowing the fastener to be installed without countersinking into even the hardest woods. The screw head closes the hole off with precision, leaving no damaged fibers around the head. R4 screws 2-Inch and longer have a four threaded portion of the fastener, allowing the wood to settle easily. It increases the screw’s drawing strength and reduces the friction on the screw shank that lowers the driving torque. R4 stainless steel PHEINOX screws are made from the best grade of stainless steel wire offer a limited lifetime warranty against staining and rusting.