FYI, I have a 2006 Prowler and I wanted to change out the stock air filter with a K&N. Just wanting to replaced the filter not the air box I called my local dealer. The part number they are calling for does not fit. It does not have a proper groove cut in the filter. I went to K&N's web site and did a search by model I came up with a part number of AC-4004. I called the dealer and he confirmed with his K&N rep. So 2006 650 Prowler K&N air filter replacement is a AC-4004. Hope this helps guys and gals.