Here's my filter setup. Made for me by these guys http://www.uniflow.com.au/
Yes I know, its a bit dirty
With the top lifted off. Still nice and clean underneath.
The underside. They use your old paper filter, cut the guts out of it and fit their own. As the fillter is flat, spares can be carried without taking up much space. I used to find with the paper filters there would always be a fine layer of dust on the inside of the airbox. Not so with the foam type.