Replace or upgrade your worn chain and sprockets with this market leading sprocket kit featuring quality JT Sprockets and D.I.D chain brought to you by THS Moto. Note the chain may need to be adjusted to length using a chain breaker tool. This Sprocket Kit contains a 13 tooth front JT sprocket and 49 tooth rear JT sprocket with a 520ERT3114G 114-Link 520ERT3 Race MX clip link DID Chain Fits: Yamaha YZ250F 2005-2009