K&N and BMC filters are widely used by 12 riders. In the case of the 12, either of these work better than the stock filters, which have a well-earned reputation for letting a fair amount of fine particles coat the inside of the airbox. Some of the early K&Ns were reported to not fit well. Never heard a bad word about BMC. I have K&Ns and they fit well.
When used with a full exhaust system, the flow difference vs. stock is significant enough that there are separate Dynojet maps for bikes with stock or aftermarket filters....