Different Size Filters
My 2 cents worth...The size of the TRD oil filter happens to be pretty close to that of the old 20R engine of the mid `70`s, the 3B motor of the `80`s and the 5MGE motor of the `80`s, and probably more. This filter is close to the same filter found on most Ford`s from the `60`s to the mid `90`s. Also a shorter version can be found on most Chrysler products from the early `90`s to present. The size of the thread and gaskets are the same for these filters, although there might be some diferences in the valving or the filter element itself. So, in theory, aftermarket companies will have a filter much like the TRD filter.