Snappy has set the standard for countersink bits! These bits not only drill the proper size pilot hole for the screw but will countersink (82 degree) for the screw head and counterbore (3/8” or 1/2″ diameter) for the plug! The large gold set screw on the side of each bit ensure a tight bit fit with no slip, allows for easy adjustment of the drill bit protrusion for different screw lengths and easy drill bit replacement (any standard drill bit will work). These bits are made of alloy steel that is thru hardened for long life and can be re-sharpened. These particular bits have shanks specifically sized to fit the Centrotec Chucks on the Festool Drills. All made in the U.S.A.!