Pep Boys around here only sells the Royal Purple filter (No K&N--Bill, I asked. They didn't have a reason.). I just put mine on yesterday, and while the number eludes me (couldn't find it on their site; I had to use the lookup book at PBs), it fit on perfectly.
The only difference, besides the purple color, was the fact that the RP filter lacks the nut welded on for use of a normal wrench, but I've never had to use a wrench on the trac's filter. Hand tight and hand loosen has worked thus far.
On a tangent, has anyone done these bypass filters?