These are the first bits of this type that I have used so I may not be too competent to give an opinion on this product. They work very well for what I use them for, mainly drilling river rock, but I've had some issues with harder rocks like agate. Also, the bottom edge wears out pretty quickly, so there are only a few holes per bit, but they're very affordable, so if you don't mind changing bits often. Overall I am happy with this product and will most likely purchase more at some point. I turned it on its side (and probably abused it) after the cutting edge wore down because the diamond sticks out nicely on the side of the shank, so I use what's left to shape the stone. Seems to be working fine.