These professional quality countersinks feature a single-flute 82° cutting head for fast stock removal and chatter-free drilling. This uniquely designed cutting edge shears through wood and other material for a perfect cut. Each one has a ¼" shank and is for use with your drill press or electric drill. Includes a ¼", 19/64", 11/32" & 3/8" countersink with custom wood case. For use with no. 4, 6, 8 and 9 screws.