500i Air Filter StackWestcoast Saw Stihl 500i stack system provides superior filtration in an easy to install kit. Components include billet aluminium housing and Uni Filter Foam Filter with clamp. NOTE: This air filter stack does not fit under the hood. Filter MUST be properly OILED before installation. Without sufficient oil the air filter will fail to stop harmful dirt particles from entering your engine which will result in decreased performance and serious engine