the stock paper element is very restrictive to power I suggest aftermarket. though what I am saying from experience, from my last trail ride. DO NOT GO WITH MOOSE AIR FILTERS, they are a peice of garbage. It gave me good power on the road, but this element apparently seals very poorly to airbox. After last Florida Swamp run my carb got loaded with sand, and is currently in bad condition do to MOOSE´s POS. please read this warning and take caution on which airfilter you up grade with. It is not a good thing to have to rebuild a 2004 motor with 2400 miles on it because of someones shitty aftermarket parts.