K&N currently does not carry an air filter for the CBR250. I have found on my other bikes and cars that using one does provide better top end engine responsiveness. Not a night and day improvement, but maybe 5 mph higher max speed. Seems like that would be of interest to many for the CBR250. If you want to help, get on www.knfilters.com/products_needed/ where you can recommend to them to make one. Maybe they will offer one by the time I need to change mine.