GRK Fasteners R4 01105 Decking and Framing Screw, #9 Thread, 3-1/8 in L, W-Cut Thread, Flat Head, Star Drive, Steel

GRK's R4 self-countersinking screw has a patented 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.