['68 Newtricks]

Um, pass through I guess. It's a hose going to a can with a mesh material inside, another hose goes to the intake. The can came from eBay, originally had nothing inside (which I didn't like) so I made the incoming hose longer to reach the bottom. The air has to pass through some thick (but not dense) plastic mesh. (think more airy steel wool) Haven't put enough miles on it to know if it's helping yet.