The unique RotaStop shank guarantees a positive lock in the chuck or extension bar and a quick release. This feature is also included on the shanks for the Colt Extensions. The cutting edges are diamond ground from the highest quality raw material to give the sharpest edge and the cleanest holes. The periphery of the hole is precut before the main cutters commence work which prevents splintering. The main cutters are sectional to create smaller shavings which permits a higher drill feed speed and faster work. Running at the correct speed is very important, sizes to be run at the following speeds; 15 - 20mm run at 2000-3000rpm, 25-35mm run at 1500 - 2500rpm, 36-45mm run at 1200-1800rpm and 46-55mm run at 800-1200rpm. Suitable for end grain and side grain. All bits are 10mm shank. Made in Germany. Extensions and a 2MT adaptor is available for use with these forstners.