One of the most important components of any nitrous system, NOS filter fittings feature an aircraft type stainless steel mesh filter element to keep contaminants from attacking the solenoid and plugging the jets. The new NOS high pressure Billet Aluminum Filters (#15550 & #15552) feature a precision billet aluminum body and a cleanable stainless steel mesh filter element that has 10 times the filtering area of a standard filter. All NOS nitrous systems include Nitrous and Fuel Filters.