I have tried many mini drill sets on Amazon and hobby sites and they have all been cheap and break very easily. I'm so glad I finally found a brand to use. I use them to poke holes in polymer clay and resin pieces to insert eye hooks. I originally took a size #65 and it works fine but was a bit large for my thinner pieces and I found it nerve wracking to drill when holding the piece with my hand trying to keep it straight. I mostly use 20-24 eye hooks so I recently bought a #67. They were noticeably smaller than I was hoping for but I think I'll try a 70 or 72 now and use 67 as my largest. I can't get my parts in a vise or get things perfectly vertical, and there's a kink/stress I can't help but apply and I've NEVER had a single breakage. Haven't tried them with a cordless Dremel or a wired Black & Decker RTX, but I think they will. I highly recommend this brand. Image size #65 left #67 right