It seems like the KX500 is one of those bikes that only get updated every decade or so. deoending on the year of your bike, it should interchange with close model years. I know for my 01 model, ther are 2 gasket options from Kawasaki. A steel gasket that is .2 mm thick for high compression, and a fiber 1 mm thick gasket for lower compression (smoother low end, more overrev) For my purposes (oversized KDX) I went with the 1 mm fiber gasket. Low end was brutal, and prone to stalling, and could be a nightmare to start. The thicker gasket made it a much better trail machine.