K&N RU-3121HBK Dryflow Black Round Tapered Air Filter 3in Flange 4.5in OD 5.75H

Vehicle Fitment

• Universal Fit - Designed for performance vehicles, cold air intake systems, racing builds, and any application with a 3.00 in. intake tube requiring a compact oil-free clamp-on tapered air filter

Fitment Notes

• This is a universal clamp-on filter - verify your intake tube outside diameter matches the flange inside diameter of 3.00 in. before purchasing
• Rubber flange can be stretched up to 1/16 in. (1.5 mm) to accommodate in-between sizes or angled intake configurations
• Oil-free Dryflow design - requires K&N Synthetic Air Filter Cleaner for servicing (sold separately); do not use the standard K&N oil-based Recharger kit
• Not a direct OEM replacement for a specific vehicle - confirm fitment by measuring your intake tube diameter

Features

• K&N Dryflow oil-free synthetic media - no filter oil required, no mess, no risk of MAF sensor contamination
• Black Series colorway - stealthy black filter body for a clean, aggressive engine bay appearance
• Compact round tapered (cone) design - 4.5 in. base OD, 3.5 in. top OD, 5.75 in. height
• Ultra-strong molded pliable rubber flange absorbs vibration and provides a secure, leak-free attachment
• Washable and reusable - requires cleaning only every 50,000 miles under normal conditions
• Low-restriction design delivers strong airflow without the need for oiling
• Made in the USA
• Backed by K&N's Lifetime Limited Warranty

Specifications

• Series: K&N Black Series / Dryflow
• Shape: Round Tapered (Cone)
• Flange Inside Diameter: 3.00 in. (76 mm)
• Flange Length: 1.00 in. (25 mm)
• Flange Type: Centered (Single)
• Flange Angle: 0 degrees
• Base Outside Diameter: 4.50 in. (114 mm)
• Top Outside Diameter: 3.50 in. (89 mm)
• Height: 5.75 in. (146 mm)
• Filter Media: Dry synthetic (Dryflow) - oil-free
• Filter Color: Black
• Top Style: Rubber End Cap
• Inner Wire: No

Included Components

• 1x K&N RU-3121HBK Dryflow Black Series Universal Clamp-On Round Tapered Air Filter

Product Description

The K&N RU-3121HBK is part of K&N's Black Series lineup, featuring the company's Dryflow oil-free synthetic filter media in a compact round tapered form factor. Unlike traditional K&N cotton gauze filters that require periodic oiling, the Dryflow design delivers high airflow performance with zero filter oil - eliminating the risk of MAF sensor contamination and simplifying maintenance. Its cone profile - 4.5 inches at the base narrowing to 3.5 inches at the top over a 5.75-inch height - provides a solid filter surface area to support 3-inch intake flows while maintaining excellent filtration efficiency.

The centered 3.00 in. rubber flange mounts securely onto matching intake tubes, absorbs vibration, and can be stretched slightly to fit in-between sizes. When cleaning is needed (every 50,000 miles), simply wash with K&N's Synthetic Air Filter Cleaner - no re-oiling required. The black filter body gives it a premium stealth appearance in any engine bay build. Made in the USA and backed by K&N's Lifetime Limited Warranty, the RU-3121HBK is the right choice for builds requiring a compact, oil-free clamp-on filter with a 3-inch inlet.