3/8 in. Drive Hex, Torx, Phillips, Slotted, Square Bit Socket Set (91-Piece)TEKTON bit sockets are formed through a carefully controlled insert process that press fits S2 steel bits into the sockets for a straight, permanent connection that can't loosen over time. The bit tips are machined to exact tolerances for precise engagement with fasteners. The extra length of the long bits allows you access deep into narrow, recessed areas. Die stamped markings are permanently impressed into the socket with large, clear size numbers