Made of tungsten vanadium steel for strength and durability. Teeth are precision machined and uniformly spaced so cutting is accurate and smooth. Maximum safe speed varies with bur size and is indicated on the box. Burs measure approximately 1-3/4" long with 3/32" shank. Made in Germany. Busch burs are recognized as the world leader for premium quality burs, widely used in the jewelry industry. Busch burs are manufactured on high-tech machining centers using proven, state-of-the-art technology. PLEASE NOTE: SIZES 2.1 AND 2.3 ARE NOT LISTED IN THE ABOVE CHART. THEY HAVE BEEN DISCONTINUED, HOWEVER WE STILL HAVE A FEW PACKAGES IN STOCK.