Our 12" Long Extension or "Aircraft" drill bits are a high-speed steel drill bit made to drill holes in hard to reach places. The high-speed steel provides high strength and longevity and the 135* split-point quickly sinks the drill bit into hard metals without the drill bit "walking". They are used for general purpose metal cutting. The black oxide coating prevents chip welding and provides some lubricity for smoother cutting. Made in the USA by Norseman Drill & Tool.