I was stopped by rocks in concrete that refused to submit to carbide masonry bits (Bosch and Dewalt, both). The rocks rounded off cold chisels and just wouldn’t submit. I ordered these in hope of getting through and sure enough, made it past whatever they were made of. Was not rebar.I made the mistake of trying to drill with water in the holes. The bits stayed cool but that meant the wax plugs up the middle didn’t melt and had to be ground away by the concrete core that builds up the middle. Not a huge deal, just would have been slightly faster with less junk in the water if I’d let them heat up.I did bend one bit using a Milwaukee M12 cordless hammer drill. Don’t use the hammer function with these. Otherwise all went well and they did exactly what I wanted them to do. It was not a hot knife through butter like one of the other reviewers stated, but they did get through some serious rocks that brand name carbide bits refused to drill.