steel forging: the surfaces of the wrench is polish and electroplated with chromium Overall thickening and hardening, not easy to fracture: chromium steel, overall thickening and hardening National standard opening usage specification: The wrench opening size refers to the tolerance specified in national standard T4389-2013, which is more standardized High temperature quenching is sturdy and: High temperature tempering enhances toughness and prevents cracking Easy disassembly of screws: With high torques, it is not easy to slip or damage the nut, Manufacturer: Kaeltsyn