K&N 5/16in x 3/8in Universal Replacement In-Line Fuel Filter - 81-0300

The K&N Engineering 81-0300 Universal Replacement In-Line Fuel Filter is a clear-view inline fuel filter designed to work with both 5/16-inch and 3/8-inch fuel lines — making it one of the most versatile universal fuel filters available for carbureted and non-fuel-injected applications. Whether you're building a classic car, maintaining a motorcycle, or setting up a custom engine bay, this K&N inline fuel filter delivers transparent, at-a-glance monitoring of fuel cleanliness without requiring you to pull the unit from the line.

Key Features & Benefits

• Clear Glass Body: The glass housing lets you see directly into the filter element at any time — no guesswork about when debris has accumulated or when the mesh needs attention. This is especially valuable on builds where visual inspections between drives are part of regular maintenance.
• Dual Fuel Line Compatibility: Accepts both 5/16-inch and 3/8-inch fuel line, so you're not locked into a single application. This flexibility makes the 81-0300 a practical choice for a wide range of projects — from vintage muscle cars to custom off-road builds and powersports rigs.
• Replaceable Inner Mesh Filter: The internal mesh element can be replaced independently, meaning you don't need to buy a whole new filter assembly every service interval. This design saves both time and money over the long run compared to disposable canister-style filters.
• Tool-Free, Easy Installation: K&N engineered the 81-0300 to be easy to install with no special tools or skills required. It installs inline with your existing fuel line, making it accessible for DIY enthusiasts and shop professionals alike.
• Designed for Non-Fuel-Injected Applications: This filter is specifically designed for carbureted or non-fuel-injected setups. If you're building or restoring a vehicle with a carburetor, this is the intended use case K&N designed it for.
• Trusted K&N Engineering Brand: K&N has been a recognized name in automotive filtration for decades. The 81-0300 carries that reputation into a simple, well-constructed inline filter that performs consistently.

Specifications

• Part Number (MPN): 81-0300
• SKU: KNN81-0300
• UPC: 024844343680
• Fuel Line Compatibility: 5/16 inch and 3/8 inch
• Body Material: Glass (clear view)
• Filter Type: Inline / In-line, universal
• Inner Filter: Replaceable mesh element
• Application Type: Non-fuel-injected (carbureted) applications
• Proposition 65: Yes — this product is subject to California Proposition 65 requirements

Fitment

The K&N 81-0300 is a universal fit fuel filter — it does not carry vehicle-specific fitment data tied to a year/make/model lookup. Compatibility is determined by your fuel line diameter (5/16" or 3/8") and whether your vehicle runs a non-fuel-injected (carbureted) fuel system. It is not intended for fuel-injected applications, which operate at significantly higher fuel pressures than a mesh inline filter of this type is designed to handle.

Common applications where this filter is used include: classic and vintage cars, hot rods, custom builds, carbureted motorcycles, ATVs, and small-engine equipment with 5/16" or 3/8" low-pressure fuel lines. If you are unsure whether this filter is appropriate for your specific setup, contact the ThreePiece.us fitment team before ordering.

What's in the Box

The K&N 81-0300 kit includes the inline clear-view fuel filter with glass body and inner mesh filter element. The replaceable mesh insert is included as part of the assembly. No special tools are required for installation.

Why Buy from ThreePiece.us

ThreePiece.us has been serving automotive enthusiasts since 2014, with a team that brings hands-on expertise to every order. Here's what you get when you shop with us:

• Free Shipping: Every order ships free — no minimum purchase required.
• Affirm Financing: Break your purchase into manageable payments with Affirm financing, available at checkout.
• Expert Fitment Support: Not sure if this filter is right for your application? Our team is reachable at 813-535-5801 or via email. We've helped over 10,000 customers get the right parts for their builds.
• In-Stock Availability: The K&N 81-0300 is a regularly stocked product — no long wait times.
• Price Match Guarantee: Found it cheaper elsewhere? We'll match it. See our Price Match policy for details.

Frequently Asked Questions

Q: Will this fuel filter work with my fuel-injected vehicle?
A: No. The K&N 81-0300 is specifically designed for non-fuel-injected (carbureted) applications. Fuel-injected systems operate at much higher pressures and require a different type of filter rated for those pressures. This filter is intended for low-pressure carbureted fuel systems only.

Q: Does this filter work with both 5/16" and 3/8" fuel line?
A: Yes. The 81-0300 is compatible with both 5/16-inch and 3/8-inch fuel lines, giving it broad versatility across a wide range of carbureted builds and applications.

Q: Do I need special tools to install this inline fuel filter?
A: No special tools or skills are required for installation. K&N designed this filter to be straightforward for DIY installers — it simply installs inline within your existing fuel line.

Q: Can I replace just the inner mesh element, or do I need to buy a whole new filter?
A: The inner mesh filter element is replaceable, so you don't need to replace the entire assembly at each service interval. This is one of the key advantages of the 81-0300's design — it saves money and reduces waste over time.