These Snappy countersink drills have a huge advantage over the competition. Use these countersinks to drill the pilot hole and countersink or counterbore in one step. Large ¼" hardened set screw holds drill bit securely to prevent bit slippage. Set screws are harder then allen wrench, so the set screw doesn't strip. Easily adjust drill bit for proper pilot hole depth. Uses standard size drill bits. Alloy steel, thru-hardened to cut hardwoods and composites, can be sharpened for a long cutting life. 82 degree countersink angle allows screw heads to set tight and flush to the surface. The ¼" standard hex shank fits all quick change chucks, impact drivers, or all drill chucks.