1/4” and 5/16” hex insert Phillips ® Head Screwdriver Bits can be used for driving screws and fasteners with hand tools, corded or cordless power tools, and pneumatic tools. Phillips Head screwdriver bits are commonly used in aircraft assembly, maintenance and throughout the aviation industry.The Phillips Head screw drive is purposely designed to cam out when the screw stalls, preventing the fastener from damaging the work or the head. The quality of MRO Tools bits begins with select raw materials. Only carefully chosen, high grade tool steel is used.Each bit is manufactured to the tightest tolerances in the industry, most are even tighter than licensing agreement requirements. Our bits meet the most stringent government and military specifications.