Great Product! I use it in fairly hard clay soil with lots of roots. Thus, the drill constantly stalls due to the roots, and there is also a sudden jamming. It seems insulting, but these snails keep doing their job and run without failing. Previously, the small had to be exposed to at least 3 hours of such cumulative heavy use, and the large had to be exposed to at least 1 hour of such cumulative heavy use. A few obvious tips: Make sure the shank positions are very tight in your drill chuck. Otherwise, the hexagonal shape may get unnecessary out-of-roundness.