WLA "Army" Air Filters

Those metal block filters (filled with Brillo pad type wire mesh) are stacked on top of each other inside the square canister.  I clean them once a year, and re-oil.  You add some oil to the lower tray, and it suspends any dust, sand, rocks . . . and bugs that dare to enter.  I doubt anything ever makes it to the carburetor after enduring this obstacle course !