Cr-Mo ALLOY STEEL - Cr-Mo impact socket features with added strength, higher working temperatures and corrosion resistance. It's much stronger to stand greater impact force than chrome vanadium ones. COLD FORGING & HEAT TREATMENT - Cold forging and heat treatment greatly improve the performance of the socket with enhanced hardness, increased wear-resistance and lifespan. 6-POINT SOCKET OPENING - 6-point design provides an exact and snug fit, allowing it to apply more torque on the fasteners and avoid slipping off. RADIUS CORNER DESIGN - The lifespan of both the fastener and socket will be greatly prolonged with the torque distributed to the inwall. BLACK PHOSPHATING - A fine and dense coating brings more corrosion and wear resistance for longtime use. Founded in the 2000s, Jetech boasts a comprehensive range of tools with a strong focus on professional industrial-grade tools. Engineered for durability and performance, the Jetech 3/8 Inch Drive 21mm Standard Impact Socket is constructed from high-quality cr-mo alloy steel. Through a meticulous process of cold forging and heat treatment, this socket can withstand heavy-duty use in a variety of applications. The 6-point socket opening provides a precise fit on fasteners. Easily determine the size of each impact socket with clear markings on the surface. Radius corner design protects the fastener and socket, prolonging their lifespan. With a black phosphating finish for added protection against corrosion, this metric socket is a reliable choice for any project.