Phillips insert bits 20- piece"pro-pak" bit size=#2 pack of 20 Made of high-grade S2 tool steel and milled for precise fit. Specifically built for the higher torque requirements of power tools; can be used with drill chuck or quick change chuck adapter in applications such as appliance, automotive, aviation, decking, drywall, electronics, furniture assembly, general construction and HVACR; 1/4 inches hex shank.