Here is the Napa 6270 air filter beside the genuine Onan filter. It is bigger but fits well (at least on the 6000 watt). Although it still cost $16, it appears to be a better filter at half the price of an Onan. You will have to use a 9.5 inch center rod in place of the regular 8 inch. I did find some other matches as well however: AC/Delco A527c; STP 8113; Tractor Supply LAF 8113; Fram CAK 530.