2006 Arctic Cats saw some changes to their clutching system, with the addition of larger diameter secondary clutches on some models. The Firecats and 900s were fitted with the larger secondary, but they also received a smaller diameter primary clutch as well. According to Arctic Cat, this was done to take out some of the overdrive and improve drive belt efficiency, which would improve belt life.
The larger diameter secondary was not found on the Crossfire or M-Series models, as it makes drive belt changes very difficult due to the lack of clearance (tight fit).
Overall, these changes appear to have made negligible performance differences in the field. In theory, the low end performance should have improved, but this didn’t appear to be the case in real world testing. Drive belt durability does seem to have improved, however.