The combination of a middle drill and chamfering cutter allows you to simultaneously machining the hole at 90 degrees with a single drill.
Using high speed steel (HSS) means less wear on the drill and can be used for a longer time.
If the middle drill wears out, you can easily replace it with the included L-type wrench.
The medium drill has an X-shaped thinning process that provides good adhesion and has good discharge of the cutting at the tip, which greatly extends the life of the drill.