For a comprehensive set of Long Series wire gauge Aircraft extension drill bits to NAS907 Type J standard, the CO501-6 set is exactly what you need. With all wire gauge sizes from 52 to 1 (53 drills in all), the 501-6 drill bits in the set have a low thrust design and self-centering, 135 degree split points for easier penetration. Manufactured from premium High Speed cobalt, the drills can be used in many materials, including steel, aluminum and stainless steel and have a bronze oxide finish to prevent workpiece material from sticking to the cutting surfaces of the drills, ensuring clean and accurate holes. Designed for stable drilling in hard to reach areas, the drills have a long overall length (6 inches on every drill), with short flutes.