The K&N RU-2430 is a High-Flow Original universal clamp-on air filter rated by the manufacturer at 3" flange, 5" outside diameter and 5" height. It is a round straight design with cotton gauze media and a rubber top. The manufacturer rates it at up to 99% efficiency and says the media is designed to increase horsepower and acceleration. Because it is washable and reusable, a buyer pays once instead of replacing a disposable paper element at every service, which is the practical case for choosing it over a basic paper filter.
Being universal fit, the RU-2430 suits custom cold-air builds, carburetor throats and aftermarket intake tubes with a 3-inch inside diameter rather than a specific vehicle. Its pliable rubber flange absorbs vibration and can stretch up to 1/16" (1.5 mm) to fit between sizes. It ships pre-oiled, so a DIY installer can clamp it on directly. Searches for a 3 inch flange washable cotton gauze universal air filter, a 5 inch OD clamp-on intake filter, or a reusable K&N RU-2430 replacement usually point to this exact configuration.
The manufacturer states that K&N air filters are pre-oiled and ready for use, so the filter can go in as supplied. Oil is only needed later, when you clean and re-oil it.
The manufacturer lists it as a universal fit designed for a variety of applications, not a vehicle-specific part. Match the 3" inside diameter of your intake tube or carburetor throat to the filter flange, and remember the flange can stretch up to 1/16" to fit between sizes.
The manufacturer describes its cleaning process using K&N filter cleaner, a low-pressure rinse, complete drying, and K&N filter oil, and states that this is the only approved procedure for maintaining its High-Flow filters.
Installation is a basic clamp-on job: the manufacturer describes K&N filters as easy to install, and the work comes down to seating the 3" rubber flange on the intake tube or carburetor throat and tightening a clamp so the seal is airtight. Plan for a screwdriver or nut driver for the clamp, plus K&N cleaner and recharge oil for future service. Check that the flange sits fully on the tube with no gaps, since unfiltered air leaking past the seal bypasses the media. Let the filter dry completely before oiling, and avoid over-oiling, which can foul a mass airflow sensor on fuel-injected cars.
