Set includes .5mm, .7mm, .9mm, 1.1mm, 1.4mm, 1.6mm, 1.8mm,
2.0, and 2.2mm. Drills are solid cobalt steel and outlast high speed
steel (HSS) bits 15 to 1. Drilling speeds should be between 500 and
10,000 rpm. All drilling should be done with a lubricant. The harder the
material (metal) to be drilled and the larger the hole size, the slower
the drill speed.