A good aftermarket filter is the Filtro brand. I think they are Brit: they once came out with ones that had a wrong-size seal on it, and when I contacted them about it (too loose), they immediately recalled all their filters of the type, everywhere. When they got the rubber mold 'fixed' they sent me 3 to test, to be sure: when I replied back, only then did they put them back on the market. Good guys, good filters, too. I use them now on my own 750.