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K&N Performance Air Intake System - Ford Focus ST and RS Mk2
  • K&N Performance Air Intake System - Ford Focus ST and RS Mk2
  • K&N Performance Air Intake System - Ford Focus ST and RS Mk2
K&N Performance Air Intake System - Ford Focus ST and RS Mk2

K&N Performance Air Intake System - Ford Focus ST and RS Mk2

£172.49 £229.99
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Advanced Filtration

K&N filters are designed with a less restrictive, oiled cotton gauze media that allows for a greater volume of air to flow into the engine

Made in the USA

Proudly manufactured in the USA, K&N filters use the best of American technology and in house engineering
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Delivery, Returns & Stock Information

- With popular products we will always aim to hold stock to ensure rapid delivery times across the UK.

- With less commonly ordered products we rely on drop shipping from our suppliers, this can occasionally result in delays in delivery times.

- Where a product is required urgently please contact us first before placing your order so we can check stock and delivery times to ensure no disappointment.

- Once an order is placed we aim to be in touch within 24 hours with either your delivery details or estimated time of delivery for your products.

- Need to return an item? No problem, get in touch and we can explain the next steps.

K&N UK in-stock items are delivered in 1-2 working days.

Items that are out of stock, may arrive from K&N EU - the delivery time in that circumstance is 3-5 working days.

Please contact us ahead of time to confirm.

Price Match

Seen it cheaper elsewhere? Get in touch with where and how much and we'll not only do our best to match it, where possible we aim to beat it!
Product Queries

Got a question about this product? Get in touch via our online chat or email and our team of experts will get back to you as soon as we can with an answer.
Does this fit my car?

This product is compatible with the following models and year ranges:

Ford Focus ST Mk2 ST225 (2005-2011)
Ford Focus RS Mk2 (2009-2011)

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 moulded 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. 

  • 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

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