These are very cheap drill bits so I honestly bought them. I had to drill 2 x 10mm holes about 3/8" and knew I would never need them again. I had to pre-drill the holes with a good 3/8 inch drill bit I had and enlarge the holes a bit with that drill bit, so I didn't ask much of them, but they barely managed to pull off this simple task. Their material is probably decent quality for HSS drill bits, but they were poorly sharpened and dull at the cutting points. If you just need to drill a few holes and/or drill very soft material, that might do the trick, although I doubt they'll clean holes in many items without proper regrinding. Also, I've worked in a machine shop for 3 1/2 years, so I know how to handle drills.