HTS-4A Apex #4 Hi-Torque Insert Bit, 3/8” Square Drive. Apex Hi-Torque Bits from Apex Fastener Tools are used for driving screws and fasteners with power tools, hand tools and pneumatic tools. The recess on the Apex Hi-Torque Bits was designed to provide very high installation and removal torques, very shallow recess for use on 120° and 130deg; flush fasteners in thin skins, and to reduce the need for end-load of the driver. Apex Fastener Tools has developed special alloys with attributes suited to the demands of the aerospace and automotive repair industry.