K&N High-Flow Universal Clamp-On Air Filter RE-1040 — Oval Tapered 4" Flange, Washable High-Performance

The K&N RE-1040 is a washable, reusable universal clamp-on high-flow air filter built to boost airflow and last for the life of your vehicle.

Designed for a wide range of custom and replacement applications, this oval tapered clamp-on filter (4" flange diameter, 7.5" height, 1.5" flange length) provides improved air delivery while cutting long-term maintenance costs. Its multi-layer cotton gauze media, pre-oiled finish, and pliable molded rubber flange make it durable, easy to fit, and serviceable instead of disposable. Below are common buyer questions answered clearly to help you decide if the RE-1040 matches your needs.

How does this filter affect engine performance?

The RE-1040 is engineered to allow increased airflow compared with many stock paper filters, which can improve throttle response and support modest horsepower gains when paired with a compatible intake. The cotton-gauze media traps contaminants while permitting higher flow, balancing protection and performance without replacing the filter regularly.

• Multi-layer cotton gauze media for efficient airflow and filtration
• Pre-oiled finish optimized for immediate use and consistent performance
• Tapered oval shape adapts to tight intake spaces for better fitment

What are the key dimensions and fitment details I should know?

This universal clamp-on unit features a 4-inch flange diameter, 7.5-inch overall height, and a 1.5-inch flange length—measurements that help determine whether it will seal correctly to your intake. The pliable molded rubber flange absorbs vibration and allows a secure clamp-on connection to round or tapered tubing within that size range.

• Flange diameter: 4 inches — confirms clamp sizing
• Height: 7.5 inches — ensures clearance under hoods or inside enclosures
• Flange length: 1.5 inches — helps create a reliable seal with tubing

How do I maintain and clean the filter?

K&N filters are washable and reusable, designed to be cleaned rather than replaced. Under typical highway driving, the RE-1040 generally requires cleaning about every 75,000 miles, but conditions like dusty roads may require more frequent service.

• Wash with K&N cleaning kit or equivalent filter cleaner
• Rinse, dry, and re-oil evenly before reinstalling
• Inspect flange and media for damage during each service

What build features and warranty support come with the filter?

The filter uses rugged materials and modern construction to withstand vibration, heat, and repeated cleaning cycles. K&N backs its products with a one-year limited warranty and manufactures this filter in the USA, reflecting consistent quality control and parts support.

• Durable molded rubber flange for secure clamping and vibration absorption
• Four-layer cotton gauze construction for filtration reliability
• One-year limited warranty and U.S. manufacturing

Who is this for? The K&N RE-1040 is suited to car and motorcycle owners, custom builders, and DIY enthusiasts who need a reusable clamp-on filter in an oval tapered profile that fits a 4" flange. It’s a practical upgrade for those who want improved airflow and lower long-term filter costs, especially when space constraints or aftermarket intake setups require a compact, versatile clamp-on solution.