Servicing an 848 for a friend and found this mess inside the airbox!!! Full service history by main dealers apparently. Unsealed airfilter.
Not uncommon I'm afraid Many years ago I heard about the poor sealing of tha standard air fillter and purchased a BMC, it was a toss up between that or a K&N. Both these filters have slightly bigger lips (I know some smart ass is going to make summit of that) so seal better When I was replacing I was shocked by the amount of shit on the clean side of the box, Bike had somewhere between 2-3k miles at that point Now running an MWR
This was running a standard filter but had also been distorted and crushed so had no chance - K&N going in.
I've tried them all. MWR are the only ones that work because they don't use the same design a standard. They are 2 individual filters that seal to the inlet ducts perfectly. Spotless each year I check the airbag, clean the filter.
MWR do 2 types, a race and road. The version with the separate 2 pieces as shown by @Jamiemac is the race type They also do a road which is longer and more like a conventional filter, that's what I have in mine. The road type look like this The race as already shown like this Not saying one is better than the other as I have not tried them both, just pointing it out