The K&N RU-4250 is a universal clamp-on air filter with a round tapered, conical shape. It uses K&N reusable cotton filter media and clamps onto any air inlet that matches its 3.75 inch flange diameter, making it a common choice for custom and replacement intake setups where high airflow is wanted.
Specifications:
- Type: High-Flow Air Filter Element
- Style: Clamp-On, Round Tapered (Conical)
- Base Diameter: 5.375 in
- Top Diameter: 4.375 in
- Height: 5 in
- Flange (Inlet) Diameter: 3.75 in
- Filter Media: Reusable Cotton
- Color: Red
- Fitment: Universal
- Quantity: Each
- Part Number: RU-4250
FAQ
What size inlet does the K&N RU-4250 fit?
The RU-4250 has a 3.75 inch flange diameter, so it clamps onto any intake tube or adapter with a 3.75 inch outside diameter.
Is the K&N RU-4250 washable and reusable?
Yes. It uses K&N reusable cotton filter media that can be cleaned and re-oiled instead of being thrown away and replaced.
What are the dimensions of the RU-4250?
It measures 5.375 inches across the base, tapers to 4.375 inches at the top, and stands 5 inches tall, with a 3.75 inch mounting flange.
Is the RU-4250 vehicle-specific?
No. It is a universal clamp-on filter and is not vehicle-specific. It fits any application with a matching 3.75 inch flange diameter.

