427 Sam - The screens came with the system. They are a piece of
oil resistent foam sandwitched between 2 pieces of 3/16" hardware cloth (wire mesh), all held on by the molded rubber sleeves to the top of the stack. Fly screens is a good description as the foam is fairly open mesh to allow the engine to breath. It does keep out bits of grit and the occasional screw or whatever gets dropped when working in the engine compartment. After 5 years of living on top the engine they are starting to show cracking in the rubber. Very Cool Parts sells replacements at about $200 a set. I'll wait until they get a little worse. Check their web site.
Bill