Hollow brass drills used with Diamond Drilling Compound to make holes in stones without cracking them. Gently apply drill to surface on which diamond compound has been applied. Use slow speed and let up on drill frequently. Makes perfect holes in onyx, ruby, etc. Due to large shank size, use with #30 handpiece. Must be used with Lubricant/Thinner.
Sold individually or in a money-saving set of all 4 sizes.