I replaced my stock Polaris 850 track with an M67 a couple years ago. The cost was half the price of OEM and the performance and durability have been excellent. I was worried about the extra 8 lbs. but I don't feel I lost any track speed, we run side by side runs with a benchmark 800 all year long and we didn't notice any speed loss. The break in was a little odd, the first 60 miles or so the track wanted to climb the front drivers everytime you hit the brake, I had to run it extremely tight for a while until the flexibility improved. I presently have 3,200 miles on it and it looks like new, not one missing lug or crack, I know I would have worn out another OEM track by now.