502-12 long series aircraft extension drills, to NAS907 type B standard, are manufactured from premium High Speed steel and can be used for drilling many materials including stainless steel, aluminum and steels. They have a steam oxide finish to stop workpiece material from adhering to the cutting surfaces, so you get an accurate, clean finish, and a 135 degree split point which reduces the push force needed and aids self-centering. For stable drilling in areas which are difficult to reach, 502-12 aircraft extension drill bits have a long overall length with a short flute length. They are available in letter sizes from A to Z.