Pipercross Plus BMW Car Panel Air Filter PP1923PLUS For BMW S55 & S63 Engines (F80 M3, F82 M4 & more)Pipercross Plus air filters have improved strength and rigidity, swapping out the mesh used in the regular Pipercross panel filters and replacing it with a stronger and better looking 1mm steel frame. You can really feel the difference that this change makes to the strength of the filter, even when pulling hundreds of CFM (cubic feet per minute) through the foam. The Pipercross Plus filter utilises two foams, the 20 PPI Foam and the 60 PPI Foam. The