These 1/3 in. Drive Hex Keys are made entirely from stainless steel and are designed for repeated autoclaving. Designed for use in applications that require precise torque measurement, these keys can be used directly with a torque wrench or any standard square drive. Manufactured from Carpenter 465 Stainless Steel and hardened to HRC 54, they have an overall length of 2 1/4 in. and are available in both inch and metric sizes.