We do trail building as a job and have a Hilti rock drill bit and used these heads to drill 6-12 inch thick rock. Step reinforcement for threading the reinforcement. We have a Hilti drill, which is pretty slow, but I still drilled through 3 or 4 heads, which makes about 600-750 drills. We've used both Bosch and Dewalt and to Dewalt's credit there really wasn't much of a difference in durability and Dewalt is cheaper. We had decent recovery time between holes, I just think the rock was very hard. Gave 4 stars because they are cheaper than similar Bosch bits and the Bosch bits seem to have issues with the bit socket falling out, sometimes quickly.