Consists of 10 different solid tungsten carbide drill bits made for PC board hole drilling. These came from a PC board manufacturer that closed and may have been resharpened or used drill bits. Many bits have a small collar on it and many have the size marked on it (some sizes may be metric). Bits range from big to 80 (very tiny). All shanks are standard 1/8". These will drill thousands of holes in PC boards, however you should use a drill press as flexing these tiny bits will break them! This is our best assortment- We find these bits very useful when making PC boards here at the Goldmine.