Sockets are designed to extend the life of fasteners The socket radius corner grabs the sturdy wall of the fastener instead of just the corners, resulting in less wear on the fastener. Forged from chromium molybdenum alloy steel for strength and durability. Sold individually. Metric Socket Size mm 21, Point Size qty. 6, Drive in. 1/2, Deep Well Yes, Material Type Chrome molybdenum.