i have the Praxis 9 hp model which looks to be somehwhat different than the one u are looking at. i have ground out well over 50 stumps with it, am still on the first set of teeth (i sharpen my own). can do a 12" diameter in about 20 mins. i am happy with it...i am a weekend homeowner warrior, not a pro...though i have made a few bucks doing some stumps for friends/neighbors. i am happy with mine..paid $1,000 for it used. i have done stumps over 30".....but they will take a while and alot of cursing...but will get the job done with patience.