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.
Cylinder Burs can be used like a flat file. They can remove large amounts of material quickly. Large cylinder burs are useful for grinding the insides of ring shanks to increase their size.
Vanadium Steel burs are economically priced. They cut precisely when new, but don't retain their sharpness as long as other steel alloys.