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.
Fine-Cut Burs are less aggressive (remove less material) than standard cut burs. They also produce a smoother surface on your work.
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.
Vanadium Steel burs are economically priced. They cut precisely when new, but don't retain their sharpness as long as other steel alloys.