All carbide burs are known for hardness and resultant tool life, as well as their cutting capacity. Often used on materials which are very hard and difficult to cut (such as platinum, white gold, titanium, and steel). Busch® AU style carbide burs cut more aggressively than standard carbides. Edges are more precise (making setting easier) and they produce a brighter finish.  Shanks measure 3/32" diameter and are marked with a gold band for easy identification. Please consult ANSI (American National Standards Institute) for speed recommendations. Made in Germany.