The DEWALT 7/8" x 16" x 21-1/2" 4 Cutter SDS-Max Rotary Hammer Drill Bit (DW5816) is designed for use with rotary hammer drills. It has a hardened core that resists breaking, rock-hard carbide cutter head, and a helix four-flute design that quickly removes dust and debris. Use this commercial-grade bit to bore through rock, concrete, and other masonry materials. The four cutter head increases life, durability and improves material removal.