actually, there's onli a slight difference between the original k&n and aftermarket (brother's) air filter. one, its filter element. the k&n or other TRUE performance parts have a filter element that can suck great amount of air without sucking dirt (although it is not as clean as standard air filter). but u still can have a lil bit less power than the k&n filter from abang filter for onli 1/10th of ur money. another one, many of k&n filter can be clean using pipe water and not some special air filter cleaner oil.... so, its up to u to choose what is best for u and ur money.