Raceworks AN-4 High Flow Nitrous Filter 140 MicronRaceworks AN 4 High Flow Nitrous Filter 140 Micron. Raceworks have a range of Nitrous fittings and accessories to plumb up your N2O system. From pressure sensors through hose, fittings, brackets and adapters, we have you covered. These filter housings have been carefully machined from high grade 6061 T6 aluminium and feature a stylish and durable black anodised finish. All Raceworks products come with a 2 year warranty.