I had to drill 38 holes to install a pool fence. I first tried this with a consumer grade rock drill bit and it took all day to drill about 4 inches of very hard concrete. I could smell burning insulation and the bit kept slipping in the cartridge. I wasn't happy with the bat. I borrowed a more powerful rock drill and doubled the speed to two a day. There was no burning, but there was still a little slip problem. Since renting a rock drill bit is expensive and I figured it would take a few days, I bought a decent but cheap $99 rock drill bit with an SDS chuck and drilled the remaining 35 holes. in less than an hour. The bit is still like new and I sprayed it with WD-40 to keep it going until I find more concrete that needs holes. :-)