Parts catalogs are great, but they can sometimes be wrong too, if you are close to a serial number change like my N6 is, or had several updates, like I have the long throat on mine to use the newer heads,not in your parts book unless you know it and update the number. My machine is a real guessing game when getting parts. It is easier to take off the broken_old and say match it! I was lucky enough to get a C2 that way and an F(that was 10 before the F2)it was my 50_50 machine.