Oh, and the same goes for 'Flat' replacements for the stock filter by K & N or whoever. Labyrinth filters *work*, again using the word advisedly, by forcing the air to twist and turn around the filter media. The actual 'Holes' in the filter are huge, this is why you can effectively see through them. The way they are supposed to work is that as the air twists and turns through the media any particulate matter having greater mass and therefore inertia will try to keep going straight and in doing so will collide with the oily medium of the filter's structure and stick to it.
Great theory. In practice it's pretty much useless. If you want to dust your motor, short of shovelling sand down the throttle bodies fitting a labyrinth filter is a pretty close second!