AIR FILTER - HFF4030. YZ250 F-K,L 19-20. YZ250 F-M 21. YZ250 F-N 22. YZ250 F 23. YZ250 FX-L1,M 20-21. YZ250 FX-N 22. Top quality materials and superior construction allow the filter to be used over and over again without any loss of performance.