Tooling kits include hardened steel toolholders and high speed steel inserts for turning, threading, profiling, and cut-off work. Inserts are T-15 High Speed Steel (HSS) hardened to Rc 65-67, then finish ground on all sides. They deliver excellent slow speed performance, precision interrupted cuts, and a smooth finish on stainless steel, Inconel, Monel, exotic metals, and plastics. Square shank toolholders and boring bars are CNC machined from 4140/4142 steel bar stock, hardened to Rc 48-50, and then black oxide coated to resist corrosion. Includes two ³/8" square bars, one right hand bar and one left hand bar, plus three high-speed steel inserts and one carbide insert that fit either bar.