Premium S2 steel bits provide optimal strength and durability to unfasten intractable screws and bit ends are sized for precise fitting. Sockets are made of enduring Chrome-Vanadium. Set Includes: 10-pc. 3/8 in. drive bit sockets (4 inch): 4, 5, 6, 8, 9, 10, 12, 14, 16, 18 mm. Storage and carrying case included.