You have found the most productive wet tile bits for porcelain we have ever encountered. Built for professional applications. you will find these bits second to none. 3/16" through 3/8" are plug style bits with 3/8" shank to be used in a hand held drill. 1/2" and larger have 5/8-11" threads to fit a variable speed grinder with approximate 2,000 to 4,000 RPM speed, and all have an overall drill depth of 3cm