GRK's R4™ self-countersinking screw has a patented underhead with saw-blade like cutting teeth and six self-contained cutting pockets. They together 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 kind of design enhances the R4's versatility by allowing the fastener to countersink into even the hardest woods. The head of the screw closes the hole off with precision leaving no damaged fibers around the head.