Review on Diamond Granite Porcelain Ceramic by Oudtinx by Michael Wehrman

This is the worst crap I've ever seen. I just had to drill a hole. I'm even afraid to use them. The diamond coating doesn't even cover the entire rim. In some sections you can see right through it. If you just need to cut a hole in something soft like marble, this might work. Don't try to use them on glass unless you're afraid of breaking the glass. I won't even open the bag and try to use it. And it costs me more to send them back than the refund is worth.