I purchased a set of Iron man sprockets NOV 5 2003 and a DID 520 ERT(2003 KX 250). I had to replace the chain in 6 mths,but the counter and rear was still holding.Counter was hooking at 8 mths,I sent it in no questions asked and had a new one in 2 weeks.The rear is still holding I have about 3 weeks left to wear it down for a replacement. It doesn't look like I will be sending it in,these sprockets are absolutely going on any bike I have.I do service my chain and sprockets after every ride even if the bike isn't washed,but I have never seen sprockets wear like the Iron mans. I ride a couple of sand tracks along with some hard pack atleast 2 times per week. I also like how the counter sprocket sits on the splines of the shaft nice snug fit. Dirt tricks is the company that puts them out and I have to say this is one hell of a after market product!!!!!!!!!!!!!