Magnetized to hold fasteners securely during installation and removal. Chrome-Molybdenum alloy steel for long life. Fully guaranteed. Radius corner design causes the socket to grab the sturdy wall, or flat of the fastener instead of grabbing the corners, resulting in less corner wear on the fastener. Comes in a heavy duty blow molded case Set includes: 3/16", 7/32", 1/4", 9/32", 5/16", 11/32", 3/8", 7/16",1/2", 5mm, 5.5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm and 15mm, 1/4" Dr. Universal Joint and a 1/4" Dr. 2" Extension.