K&N® 33-2304 - 33 Series Panel Red Air Filter (8.75" L x 8.563" W x 0.938" H)

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Product Details

K&N Air Filters

33 Series Panel Red Air Filter (33-2304) by K&N®. K&N's replacement air filters are designed to increase horsepower and acceleration while providing excellent filtration. K&N makes over 1,200 different replacement air filters for the majority of vehicles on the road. These filters are washable and reusable and are custom designed to fit into your existing factory air box. Their drop-in design means adding performance is simple. With most vehicles you simply remove the disposable air filter and replace it with a K&N. See applicable instruction sheet for details. K&N stock replacement air filters for street vehicles are covered by K&N famous K&N Million-Mile Limited Warranty and will be the last air filter your vehicle will ever need.

K&N - F.A.Q.K&N - Air Filter CleaningK&N - Warranty


Filter Types: Direct Fit Filter
Filter Shape: Panel
Filter Style: Non-Flanged
Filter Color: Red
Filter Outside Width: 8.563"
Filter Outside Length: 8.75"
Filter Height: 0.938"
Air Filter Material: Cotton Gauze
Filter Re-Oiling Amount: 1.06oz


  • Designed to boost horsepower and rate of acceleration
  • Can be cleaned and used again
  • High air flow with exceptional filtration
  • Lasts up to 50,000 miles before cleaning is required depending on driving conditions
  • Works with original equipment manufacturer vehicle electronics
  • Emissions legal in all 50 US states
  • Will NOT void vehicle warranty
  • Million Mile Limited Warranty®


  • 1 Air Filter

Most air filters on the market are a compromise. Many high-performance filters deliver better airflow, but sacrifice filtering ability and engine protection in the process. OEM filters, which are usually made of paper, filter adequately but at the expense of airflow. And airflow decreases as these air filters become dirty. Not so the K&N air filter. K&N air filters increase airflow without decreasing filtration ability, and the increased airflow remains consistent throughout the filter's service interval. The secret is in the K&N filter's construction.

K&N's initial goal was to develop a filter that would deliver increased airflow during dirty, dusty off-road racing conditions. Increased airflow improves the efficiency of the combustion process, increasing horsepower and torque. But just increasing airflow without ensuring adequate filtration under those conditions would result in a ruined engine. K&N's solution was a filter design consisting of 4 to 6 layers of cotton gauze sandwiched between two aluminum wire screens. The cotton is then treated with a specially formulated grade of oil that causes tackiness throughout the cotton’s microscopic strands. The resulting K&N filter not only delivers increased airflow while trapping dirt particles that could harm your engine, that level of airflow is maintained even as the filter gets dirty. The layers of oiled cotton fibers in the K&N filter trap dirt particles that are smaller than the holes in the filter media. The thickness of the layers also allows the K&N filter to trap dirt and dust on many levels, trapping more dirt without decreasing airflow. Contrast this with a paper filter that only traps dirt on its surface; as the surface area becomes clogged, the airflow rate goes down.

Each K&N air filter is custom designed to fit into your existing factory air box. The K&N filter is economical because it's the last air filter you'll have to buy for your car. It can be washed and reused many times, and since you can usually drive up to 50,000 miles between servicing, you won't have to clean it very often. And every K&N filter is backed by K&N's Million Mile Limited Warranty. By the way, check the CARiD reviews and read what the customers think of K&N porducts.

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.

Part Number:

Warranty Information

K&N O/E Replacement Air Filters and Air Intake Systems purchased from Authorized Dealers are backed by a Million Mile Limited Warranty when used primarily on paved roads and on vehicles for which they were designed. If one of these products ever fails to provide complete satisfaction, K&N will replace it.

K&N Aftermarket Air Filters should be cleaned every 50,000 miles for normal highway use, more often in dusty conditions. Cleaning should be done with K&N cleaner and air filter oil (or comparable air filter cleaner and oil). Use of compressed air, or chemicals not specifically designed to clean and re-oil cotton air filters (i.e. gasoline, transmission fluid, motor oil, lightweight oil, or diesel fuel) will void the warranty. Any damaged, abused or modified K&N Air Filters will not be warranted.

Any K&N product returned to K&N will need a Return Goods Authorization number and must be sent at customers' expense along with proof of purchase.

Any defective K&N Air Filter properly returned to K&N will be replaced. K&N reserves the right to determine whether the terms of the warranty, set out above, have been properly complied with. In the event that the terms are not complied with, K&N shall be under no obligation to honor this warranty. K&N will not be responsible for any indirect, consequential, special, contingent, or other damages.

K&N wants to make sure that when you buy a K&N Lifetime Air Filter or Air Intake System, you can be confident your vehicle's warranty will not be impacted. K&N also want you to feel confident that even if you experience difficulties with a dealership repair department, K&N will step-in and resolve the issue, so you won't have to. Therefore, K&N makes the following Pledge: K&N pledges to their customers that they will not be taken advantage of and charged for a repair due to a manufacturer warranty denial blamed on the presence of a K&N product.

Magnuson-Moss Warranty Act:
Legally, a vehicle manufacturer cannot void the warranty on a vehicle due to an aftermarket part unless they can prove that the aftermarket part caused or contributed to the failure in the vehicle (per the Magnuson Moss Warranty Act (15 U.S.C. 2302(C)) Learn More

Vehicle Fitment

2017 Subaru Forester 
2017 Subaru Legacy 
2017 Subaru Outback 
2017 Subaru WRX STI
  • 2.5L
2016 Subaru Crosstrek
  • Base / Limited / Premium / Sport / Touring
2016 Subaru XV 
2016 Subaru Forester 
2016 Subaru Impreza 
2016 Subaru Legacy
  • 2.5L / 3.6L
2016 Subaru Outback 
2016 Subaru WRX STI
  • 2.5L
2015 Subaru Forester 
2015 Subaru Impreza 
2015 Subaru Legacy
  • 2.5L / 3.6L
2015 Subaru Outback 
2015 Subaru WRX STI
  • 2.5L
2015 Subaru XV Crosstrek
  • Base / Limited / Premium / Sport / Touring
2015 Subaru XV 
2014 Subaru Forester 
2014 Subaru Impreza 
2014 Subaru Legacy
  • 2.5L / 3.6L
2014 Subaru Outback 
2014 Subaru Tribeca 
2014 Subaru WRX / WRX STI
  • 2.5L
2014 Subaru XV Crosstrek
  • Limited / Premium / Sport / Touring
2013 Subaru Forester
  • 2.5L
2013 Subaru Impreza 
2013 Subaru Legacy
  • 2.5L / 3.6L
2013 Subaru Outback 
2013 Subaru Tribeca 
2013 Subaru WRX / WRX STI
  • 2.5L
2013 Subaru XV / XV Crosstrek 
2012 Subaru Forester
  • 2.5L
2012 Subaru Impreza 
2012 Subaru Legacy
  • 2.5L / 3.6L
2012 Subaru Outback 
2012 Subaru Tribeca 
2012 Subaru WRX / WRX STI
  • 2.5L
2011 Subaru Forester
  • 2.5L
2011 Subaru Impreza 
2011 Subaru Legacy 
2011 Subaru Outback
  • 2.5L / 3.6L
2011 Subaru Tribeca 
2010 Subaru Forester
  • 2.5L
2010 Subaru Impreza 
2010 Subaru Legacy 
2010 Subaru Outback
  • 2.5L / 3.6L
2010 Subaru Tribeca 
2009 Subaru Forester
  • 2.5L
2009 Subaru Impreza 
2009 Subaru Legacy 
2009 Subaru Outback 
2009 Subaru Tribeca 
2008 Subaru Impreza 
2008 Subaru Legacy 
2008 Subaru Outback
  • 2.5L / 3.0L
2008 Subaru Tribeca 
2007 Subaru Legacy
  • 2.5L
2007 Subaru Outback 
2007 Subaru Tribeca 
2006 Subaru Legacy
  • 2.5L
2006 Subaru Outback 
2006 Subaru Tribeca 
2005 Subaru Legacy
  • 2.5L
2005 Subaru Outback 

Product Reviews


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K&N® - 33 Series Air Filter
K&N® 33-2304 - 33 Series Panel Red Air Filter (8.75" L x 8.563" W x 0.938" H)
Average Rating: 4.9 of 5
4.8 of 5
K&N® 33-2304 - 33 Series 33 Series Air Filter
K&N® 33-2304 - 33 Series Panel Air Filter
K&N came as described. Easy to install.
SPosted by (Tampa, FL) /
2015 Subaru WRX
Was this review helpful for you? Yes
5 of 5
K&N 33 Series Air Filter
K&N® 33-2304 - 33 Series Panel Air Filter
Initially noticed an almost 2 mpg increase before the computer adjusted to the new airflow. Now, the gas mileage is back to normal, but there is a bit more power.
KPosted by (Bellevue, NE) /
2011 Subaru Legacy
Was this review helpful for you? YesThis review was helpful for 4 users!
5 of 5
K&N Air Filter
K&N® 33-2304 - 33 Series Panel Air Filter
Great value and bump in both performance and mpg. I always install these type filters in my vehicles. Helps your engine to receive proper amount of air to provide enhanced performance. They really do pay for themselves in just a couple of years of use.
BPosted by (Clayton, NC) /
2011 Subaru Outback
Was this review helpful for you? YesThis review was helpful for 4 users!

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