Review on Uxcell Metric Diamond Coated Twist Cutting Tools by Trevor Blazis

I have been using diamond tipped twist drills to drill holes in 1-2mm thick dichroic glass for twenty years and usually get 50 to 200 holes depending on the drill bit, which varies quite a lot, but works. My usual supplier had failed so I tried these that claimed to drill glass tile and more. They didn't even break the glass surface and were 100% useless for drilling holes in anything but wood or soft material. I tried them right away (in a drill tank filled with cold water) and they were all completely ineffective on glass, agate, ceramic tile and even soft labradorite. They are only suitable for reaming already drilled holes and no more.