I have a set of S&b ( similar to k&n ) conical filters with chrome end caps, I had them fitted to my 500/4 for a few weeks, bloody awful things, fit fine etc, but, outside pair get damp and the bike then runs rough, even worse in snow and ice. Not sure where they are exactly now, handy to bench test an engine but truly a pain in the backside to live with. Also a job and a half to get jetting right. Best system I have had was a stock setup right back to the filter box, then a genuine K&n filter that is about the same size as the stock filter box. That released a few more horses, though I suspect it was rejetted to suit and ran a very free flowing exhaust.