Only made one hole plus 30 minutes - not much diamond dust compared to other bits I've ordered that run away compared to this junk. And yes I had the tank filled with water the whole time, I made the next hole with a grinder and made the round hole 1/2 inch smaller, it took the same amount of time (maybe less) to do it with a grinder machine -- a square hole would work and take less time -- but I wanted to see if I could make a round hole -- do not purchase this item