Tap holding sockets, female square drive, SAE from Apex Fastener Tools, formally Cooper Tools. Apex sockets have hex tolerances that are on average 48% tighter than DIN and 35% tighter than ANSI requirements. With Apex you are assured of an exact, sure fit. All Apex sockets have the tightest tolerances for straightness and concentricity in the industry. High strength fasteners in demanding situations, like those found in the automotive and aviation industries, often require the use of an impact wrench or impact driver to deliver the amount of torque required to tighten or loosen them. Quality design and construction give Apex sockets a long service life and durability. Remember, universal wrenches, extensions and adapters are not to be used with impact drivers.