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.
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.