Forged from the finest chrome molybdenum alloy steel - the best choice for strength and durability. Ideal for working in tight areas. The design drives the side of the fastener instead of the corner. Provides increased strength, but also avoids rounding of rusted or damaged fasteners. Fully guaranteed No doubt, Sunex tools offer one of the most complete and toughest Impact Socket lines around. This 1/2" drive 21mm 6 point extra thin wall deep socket is designed to tackle the toughest jobs with solid durability and keeps them pounding job after job. Also it features a radius corner design, causing the socket to grab the sturdy wall of the fastener instead of grabbing the corners, resulting in less wear on the fastener.