Review on BQLZR Diamond Coated Rotary Jewelry by David Norwood

I tried using them to etch glass and one bit took less than five minutes before all the diamond coating was gone from the tip. I use a drip irrigation system to keep the drill bit and glass cool so I know the diamond coating isn't from overheating. I would return them, but the hassle, not to mention the time, gas, and materials for a $10 refund is absolutely not worth it. It's just as cheap, poorly made junk as most rotary drills on the internet. I won't buy this again.