Will an 06 520 kit work on the 03 through 05 ? They sent me an 06 kit...your stock 06 R6 chain is a 525. not much heavier than a 520 setup. unless you are radically changing your gearing or racing and every little bit helps, your stock chain with a -1/+1 sprocket setup will cost you less, last longer and provide all the gear you will ever need on all but the tightest of roads. good luck and if you choose a new chain, be sure and get the press on master link and not the clip style. they are much safer.