Features and Benefits: Manufactured from chrome vanadium steel Heat treated for additional strength and durability KTI sockets are designed and crafted to take on the toughest jobs with solid performance Size and part number hard stamped for easy identification Made of heat-treated chrome vanadium steel for durability. Our sockets feature high-polish chrome finish which protects the tools from the harsh working environments found in today s workplace. Lifetime warranty. All sockets are marked with part number and size for ease of use.