K&N 6in Universal Air Filter - Universal PDM_lowering-springs The texture inside the bore

The texture inside the bore holds grease in place against the bar surface

Verus was able to achieve this by creating a large pressure delta between the top and bottom surfaces

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Gemini Cat-Back Exhaust with Titanium Tips for the 2003-2009 Nissan 350Z

K&N 6in Universal Air Filter - Universal PDM_lowering-springs The texture inside the boreKandN 6in Universal Air Filter Universal The K&N 6" Universal Filter is available for those of you who need a replacement filter for your existing cold air intake, or it could work with a custom application. K&N has set the standard in filter technology and continue today to make filters that will last the life of your vehicle. Because this is a cold air style filter, users will see improvements in horsepower, torque, and throttle response.