They actually used to manufacture the filters for K&N but K&N wanted to save a few bucks so they switched manufacturers and thats when their filters went to s*$tFWIW, HiFlow is an OEM manufacturer, who provides OEM filters to a number of manufacturers. It is very possible that they actually manufacture the OEM filters for either the R6 and/or the GSXR. They are also TUV certified (AFAIK, the only filter manufacturer that is). Were it not for the "nut", I'd probably just get OEM also, but I also like having the end nut it being pre-drilled for safety wire.