The purpose behind the fancy $3 covers (keeping EM and RF interference out) has always seemed a bit fishy to me. If the goal is to keep dust and pet hair out of your jacks, I'd certainly prefer the $0.35 plastic caps. On the other hand, my pair of fur factories (a 20-pound persian cat and a 15-pound Maine Coon) have put a fair bit of light, fine cat hair into the area behind the equipment rack as well as around the computer, and the only times I've noticed fur getting into things has been through the ventilation openings. Even that has been mainly the computer, which has a fan to draw the fur in. I suspect the LFM-1's ports have sucked some in as well, although I haven't tipped it over to check. Very little fur has penetrated to inside the equipment rack.