Master Mechanic, 1/2"Dr 21mm Imp Shallow Socket. 1/2 in. drive sockets are manufactured from chrome molybdenum alloy steel and designed to withstand rigors of heavy duty use. Size markings have been hard stamped into the sockets for quick and easy identification that will never wear away. Each socket features chamfered lead-ins on both ends allowing for easy attachment to drive tools and placement onto fasteners.