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. Drive in. 1/2, Material Type Chrome molybdenum, Metric Socket Size mm 21, Point Size qty. 6, Deep Well Yes.