They are probably the best value out there right now. Lots of grip and no heat cycling issues. If you take care of them, they will last 3-4 DE days. You'll need to flip (inside->outside) them after about 2 days. Running them at 40-42psi (after a cool down lap back in the paddock) helps with the outside edge wear.
Britax Carseat | Diaper Kit | Redneck Cutouts | Turner Studs | Bassified Individual Audio