3/32" dia. shanks are the jeweler's preferred standard for burs and small rotary tools. They fit the adjustable chucks found on most flexshaft handpieces as well as 3/32" handpiece collets.
Carbide Steel burs maintain their sharpness longer than any other steel. They are more brittle than carbon steel and hss and are more likely to break or chip if mishandled.
Round Burs are useful for de-burring or enlarging holes, carving recesses for sweat soldering, and refining stone settings. Because of their shape they can be used at any angle.