When I got my R42 it only had the short round-end chaffer and I was a little reluctant to run corn with it but dealer said that was all I needed. Well, it seemed to do a very good job but I still thought I would like to try a long-toothed corn chaffer. After spending $550 on the new chaffer, I used it one day and switched back to the old chaffer. In my opinion, the short round-tooth does a much better job of cleaning out the cob. I did do the chaffer mod on mine.