K&N's 57S Filter element only, is supplied with a rubber bung which once removed increases waste gate turbo chatter noise! it can be easily replaced if you require a quieter driving experience. Focus Mk2 RS - fits with standard Airbox or with standard Airbox fitted with mountune Airbox lid or J1 Airbox lid Focus Mk3 ST250, Zetec S 1.6 & 1.6 Eco Boost, 1.1 Eco Boost AutoSpecialists sale price, RRP £92.50 our price £89.95 K&N Performance FILTERS increase horsepower and acceleration by dramatically reducing air flow restriction caused by the original factory design. They come with K&N's Million-Mile Limited Warranty. 57S series air-filter replace the factory air filter housing with a fully enclosed injection modified air box containing a reusable K&N air filter. Installation is easy as they are specifically engineered to use factory holes and mounting points. No additional hardware, cutting or drilling is required
