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.
High Speed Steel (HSS) burs strike a balance between cost and durability. They maintain their hardness (temper) better than vanadium steel and cost less than carbide steel.
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.