This tool is used in place of the standard 5/32" hex key that is furnished with your lathe or milling machine. Its large plastic handle is more comfortable and provides better leverage than the shorter standard key. Also, because of its larger size, it is easier to spot on your workbench when you want to use it. The Sherline name is molded into the handle to identify it. This T-driver will quickly become your most often-used tool.