k-n air filter

[Breeze3at]

Glider is correct, but if you are still confused go to ebay and search "harley k&n air filter", then "big sucker air filter", the pictures will help see the difference. There's a difference between the shape of the filters for the stock air backing plate/box, and the big sucker backing plate.

 

[glider]

There's a post in the self help area that will show pics of the same thing. The arlen ness filter looks just like the HD0800 at the bottom.

K N Air Filters - Harley Davidson Community