K&N Drop-In Air Filter Ford Focus ST 2013-2016
K&N's replacement air filters are designed to increase horsepower and acceleration while providing excellent filtration. K&N filters are custom designed to fit into your existing factory ST air box for simple, fast installation. K&N stock replacement air filters for street vehicles are covered by a Million-Mile Limited Warranty. K&N Filters use oil to provide filtration, and can be washed and recharged using the K&N cleaning kit (sold separately).