K&N Engineering · New
K&N Universal Custom Air Filter - Oval Shape 9.313in OD / 2.375 Height
MPN E-3988 · Store SKU knnE-3988
Supplier stock checked 11/7/2026, 8:34:45 AM UTC. Adding a part does not reserve it.
Request a return within 30 calendar days after delivery. New parts must be unopened and unused.
Shipping & returns ↗This policy does not limit rights required by law.Free standard shipping on eligible parts orders of $100 or more. Oversized and freight items excluded. Fitment, taxes, availability and final totals are confirmed before payment.
Product details
The K&N replacement air filter for RK Series air cleaner assemblies is designed to increase horsepower and acceleration while providing excellent filtration. The air filter is washable and reusable and designed to be used as a replacement air filter for specific K&N RK Series air cleaner assemblies for Harley-Davidson motorcycles. The air filter is covered by the famous K&N Million-Mile Limited Warranty. The K&N replacement air filter for RK Series air cleaner assemblies, designed for Harley-Davidson motorcycles, are designed to increase horsepower and acceleration while providing excellent filtration. REPLACEMENT ELEMENT; RK-3952; RK-3953 Custom Air Filter
Manufacturer fitment & guides
Check E-3988 against the manufacturer’s application information below.
A manufacturer application guide is not available for this listing. Request the exact application from JuiceBuilt before payment.
Part-specific notes
- Emissions acknowledgement required before purchase.
- California Proposition 65: Y
