Sockets that use splines to make contact with the surfaces of the fastener. The ball detent on the ratchet holds the socket firmly. The ratchet turns smoothly. The gear teeth hold securely. You get sizes: 18mm, 17mm, 16mm, 14mm, 13mm, 11mm, 10mm, 9mm, and 8mm. In S.A.E you get: 3/4″, 11/16″, 5/8″, 9/16″, 1/2″, 7/16″, 3/8″, 5/16″ and 1/4″. This set works perfectly!