Focus ST 2013+ K&N 57S Performance Airbox without Intake Pipe with Lid

The 57S Performance Airbox gives you the best of both worlds: Increased airflow and performance with an OEM style airbox. With the filter enclosed in an airbox, induction noise is greatly reduced. The airbox also protects the filter, so there's no need to worry about driving in extremely wet or dusty conditions with an exposed filter. Yet you still get vastly improved airflow compared to your stock airbox. How do they do it?

K&N improves airflow by installing the largest conical shaped K&N filter that will fit in the airbox. The large increase in filter area over the stock air box filter results in a huge increase in airflow as well as a greater capacity to capture and hold dirt. The airbox also includes a custom engineered velocity stack that's designed to smooth and straighten airflow for even more power.

The 57S Performance Airbox is injection molded for extra strength, consistency and durability. It's designed to use the factory mounting holes, so no additional hardware, cutting or drilling is required. The air box has a removable lid for easy access to the K&N air filter when cleaning is required.

K&N uses a dynamometer to design its air intake kits to make the most horsepower possible. But their power figures aren't based on just one vehicle, but rather an average of runs by a number of vehicles. This means repeatable numbers and horsepower claims you can count on.

Every 57S Performance Airbox comes complete with everything necessary for installation, including comprehensive installation instructions. The K&N filter can go up to 100,000 miles before cleaning is required. And the K&N air filter is guaranteed for one million miles.

K&N® is the inventor and leading innovator of reusable cotton gauze filter technology for automotive applications. The first K&N filter was conceived for racing over 40 years ago and a performance enthusiast mindset continues today throughout all levels of the company. K&N is the sales and brand leader for performance filters, including an extensive line of factory replacement filters and performance air intake kits. The company actively promotes the environmental, economical and performance advantages of long-life reusable cotton gauze filters.