Review on Uxcell A14082700Ux0306 Spiral Tungsten Carbide – High-performance Cutting Tool for Precision Machining by Matt Ellis

These are good parts, of course. They are MUCH better than what you get when you order a cheap little hand drill and are pretty durable. So far I've hit 4 out of 10 but I can't say it's because of the drills. They're fast and sharp, but after drilling 40+ small holes in your first PCB, you begin to understand why so many people only pay for things from the factory.