aFe 21-91109 Magnum FLOW Pro DRY S Air Filter 6.5x4.75 in Momentum Intake 9 in

Vehicle Fitment

• Replacement filter for aFe POWER Momentum cold air intake systems specifying the (6-1/2 x 4-3/4)-inch oval flange filter
• Compatible with any intake housing using a matching (6-1/2 x 4-3/4)-inch oval flange inlet - confirm dimensional compatibility with your specific application before ordering
• Companion media variants in the same physical dimensions: aFe PN 20-91109 (Pro 10R ten-layer oiled cotton gauze) and 72-91109 (Pro GUARD 7 seven-layer oiled)

Fitment Notes

• The 21-91109 uses a large oval dual-dimension flange - the (6-1/2 x 4-3/4)-inch inlet is not a round opening. Confirm your intake system uses this specific oval flange geometry before ordering.
• The filter features an inverted top design - the (9 x 7)-inch top opening is inverted rather than closed, exposing additional filter surface area at the top for increased airflow capacity and extended service intervals.
• The filter body includes molded-in expanded metal - providing structural impact protection that prevents filter collapse under maximum airflow load conditions.
• This is the Pro DRY S oil-free version - no filter oil required at installation or after cleaning. For the oiled Pro 10R version in the same dimensions, order PN 20-91109.
• Sold individually - one filter per package.

Features

• Pro DRY S Three-Layer Oil-Free Synthetic Media - Maximum Convenience: The 21-91109 uses aFe's Pro DRY S filter media - three layers of progressively finer mesh oil-free synthetic material delivering high airflow performance and effective filtration without requiring filter oil. The progressive three-layer construction provides excellent filtration efficiency and consistent flow performance even as the filter accumulates contamination between service cycles. No re-oiling required after cleaning.
• Massive Oval Dual-Dimension Filter Profile - Highest Airflow Capacity: The large (6-1/2 x 4-3/4)-inch oval flange expanding to a (9 x 7)-inch base across 9 inches of height makes the 21-91109 one of aFe's largest Momentum intake replacement filters. The (9 x 7)-inch base provides exceptional filter face area to match the high airflow demands of Momentum-series intake systems on diesel trucks and high-output gas engines.
• Inverted Top Design - Extended Service Intervals: The (9 x 7)-inch inverted top exposes additional filter media surface area at the top of the filter - rather than sealing to a closed cap - effectively increasing the total usable filter surface area and extending the service interval between cleaning cycles.
• Molded-In Expanded Metal - Impact Protection: The filter body is surrounded by molded-in expanded metal that provides structural protection against direct impact and prevents filter media collapse under maximum airflow load or boost conditions - an important feature for performance diesel and turbocharged gas applications where intake vacuum forces are highest.
• Rounded Deep Open Pleats - Outstanding Dust Holding Capacity: The rounded, evenly spaced deep open pleat design maximizes usable filter media surface area across the full 9-inch filter height - delivering excellent dust-holding capacity and consistent airflow performance over extended service intervals.
• 100% Polyurethane Base and Top - Long Filter Life: The polyurethane base and top maintain their original molded shape across the full operating temperature range of the engine bay - resisting degradation from repeated heat cycles, fuel, and oil exposure over the filter's service life.
• Washable and Reusable: Clean with aFe's Power Cleaner (PN 90-10601), rinse with water, and allow to fully air-dry before reinstalling - no re-oiling required. Multiple cleaning cycles are supported.

Specifications

• Part Number: 21-91109
• Brand: aFe Power (Magnum FLOW series)
• Product Type: Pro DRY S Replacement Air Filter - Large Oval Dual-Dimension Conical, Inverted Top
• Filter Media: Pro DRY S - Three-Layer Oil-Free Synthetic
• Flange / Inlet F: (6-1/2 x 4-3/4) in - oval
• Base B: (9 x 7) in
• Top T: (9 x 7) in - Inverted
• Height H: 9 in
• Filter Style: Oval dual-dimension conical, inverted top, expanded metal protection
• Frame Material: 100% Polyurethane (base and top)
• Seal: Pliable polyurethane flange with integrated bump seal
• Expanded Metal: Yes - molded-in for impact protection
• Oiling Required: No (Pro DRY S - oil-free synthetic media)
• Washable / Reusable: Yes
• Compatible Intake Media Variants: 20-91109 (Pro 10R oiled), 72-91109 (Pro GUARD 7 oiled) - same dimensions
• Replacement For: aFe POWER Momentum intake systems
• MSRP: $140.00
• Fitment: Momentum intake replacement; universal for matching (6-1/2 x 4-3/4)-inch oval flange applications
• Quantity: 1 (sold individually)

Included Components

• 1x aFe Magnum FLOW Pro DRY S Oval Replacement Air Filter (21-91109)

Product Description

The aFe 21-91109 is a Magnum FLOW Pro DRY S replacement filter for aFe POWER Momentum cold air intake systems - one of aFe's largest intake replacement filters, using a (6-1/2 x 4-3/4)-inch oval flange, (9 x 7)-inch base, (9 x 7)-inch inverted top, and 9-inch height. The massive oval conical profile provides exceptional filter media surface area to match the high airflow demands of Momentum-series intake systems on diesel trucks and high-output turbocharged applications.

The Pro DRY S three-layer oil-free synthetic media delivers high airflow performance and effective filtration without requiring filter oil - making service straightforward and eliminating MAF sensor contamination risk. The inverted top design increases total usable filter surface area for extended service intervals, while the molded-in expanded metal surrounding the filter body provides structural protection against impact and filter collapse under maximum airflow load. Washable with aFe Power Cleaner - no re-oiling required. Companion oiled versions: 20-91109 (Pro 10R) and 72-91109 (Pro GUARD 7) in the same dimensions. Sold individually.