When I first started milling I needed a full set of bits. These are great taps that have lasted 4 years and are still working. As you'd expect, bits like #8 (1/4"-20 taps, M6 taps, etc.) are common and wear out more than others. I've used them on most aluminum alloys, but also on , and G10 split points are what you need, much more accurate hole placement.