On 3/4/2018 at 9:35 AM, HeavyRotation said: Is this the fcr 39mx adapter i need for my 400s air box, have all other parts ready to go. Yes, however that ebayer is the dude who runs a sorta shady refurb FCR site. Your choice to support that or not. I bought mine from JetsRUs, don't forget the o-ring. I do have a FCR39 SLANT, but I believe it will work just as well with the MX. http://jetsrus.com/individual_parts/021_216_su.html Sorry but I can't remember the o-ring part #. I had a spreadsheet with all the parts needed, but can't find it.