3/8” square drive extensions, 1 1/4” to 18” (32mm to 457mm) length from Apex Fastener Tools, formally Cooper Tools. Apex drive extensions 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 drive extensions 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.