3/8" (9.6 mm) / 29/68" (11.6 mm) / 1/2" (12.6 mm) / 21/32" (16.4 mm) / 27/ 32" (21 mm) with 1/2" drive made of high quality CRV steel. On both sides it has a cut for screw connections with protrusions. The YT-03316 step wrench for screw connections together with the YT-03315 ratchet is used to assemble: - connectors with external thread (male) - heating valves - lower cut-offs on radiator returns - valve extensions.