K&N 57i Series International Gen I Performance Air Intake System, Black (2013-2018 Ford Focus ST & RS)

The K&N 57S-4000 Performance Airbox replaces the restrictive factory air filter and air box lid. K&N performance air boxes are designed to dramatically reduce air flow restriction as well as smooth and straighten air flow. This allows your engine to inhale a larger amount of air than the factory air filter assembly. More air means more usable power and acceleration throughout the engine's RPM range. The 57S-4000 Performance Airbox comes with an oversized conical K&N high-flow air filter and an injection molded air box lid with the K&N logo embossed on top. The air filter can be used for up to 100,000 miles before servicing is needed depending on driving conditions. This performance air box is relatively easy to install into the air box base with commonly available tools. K&N builds these air box systems to last for the life of your vehicle and they are backed by K&N's Million Mile Limited Warranty. Some K&N 57S Series Performance Airboxes are compliant with the latest TUV emissions and sound regulations.

MORE INFORMATION

• Guaranteed to increase horsepower
• Designed to improve torque and acceleration
• Replaces entire factory air box and air filter system
• Washable and reusable lifetime air filter
• Easy to install, usually in 90 minutes or less
• Lasts up to 100,000 miles before service is required (depending on driving conditions)
• K&N Million Mile Limited Warranty

SPECIFICATIONS
Estimated Horsepower Gain: 18.29 HP @ 5500 RPM
California Restricted: Not legal for sale or use in California