Irwin Tools 1877715  Countersink Drill Bit, 3/8-Inch,  Black Oxide This product is easy to use This product is highly durable This product is manufactured in China Precision-ground 82 tip for countersinking into most machinable metals, wood or plastic Made from industrial grade high speed steel for increased durability Includes a black oxide finish for added corrosion resistance Five flute design reduces vibration for smoother drilling and extended life 1/4" round shank fits all handheld and stationary drills