I've seen on Ebay, 2 different brands/types of airfilters people have developed for the 690SM. They differ from each other, in that one has a recessed section in the center for...? I'm thinking that it must aid the flow of air thru it somehow. The other one is flat, basically a re-usable version of the OEM part.It may also flow somewhat better due to the media used in construction of the filter. The big difference is price.The one with the "recessed" section, is priced at nearly $100.USD and is imported. The other is alot less ... I know, I know ,you get what u pay for , BUT I wanna know what if any benefit one has over the other... basically, does anyone here know aerodynamics/ flow theory, etc.? There must be a reason for it ...I'm in line for a replacement exhaust as well. Anyone have one of this model? Mine has now just cleared the 1K mark on the odo, and recieved the first engine oil/filter service. It is running better after initial "break-in" ...I'm lovin' it, this mutha rolls!!What a cool bike! My first single! It takes $7-$8 USD to fill it, for 3 days commute! WOW! I'm liking that!!