Radium Engineering Fuel Filter Kit for 2016+ Ford Focus RS – TunePlus, Inc
K&N Drop-In Air Filter Ford Focus ST 2013-2016 – Import Image Racing
Ford Focus Series (07-18) DNA Air Filter R-FD16H21-01 - DNA Increased Air Flow +49.07%, DNA Filtering Efficiency 98-99% - FRD-FCS - DNA Filters - Product Details
2013+ Ford Focus ST owners – we have a drop in K&N air filter for you in stock! – ModernPerformance.com Blog
How to Replace the air filter on the Ford Focus 2014 to 2018 - YouTube