We saw a lot of chestnut oak; some of the logs are pretty tough. We had been using WM's 4 degree 1.5" .055 double hard series blades. We tried the new "turbo 7/39" tooth profile and really like them. By far the best blade we have tried in large and knarly white oak. Both feed speed and time between blade charges have improved by as much as 40% in these logs.