Koch Type GD Fiberglass Automatic Roll Filter for AAF Roll-O-Mat - 65 Foot Replacement Roll

The Koch Type GD Fiberglass Automatic Roll Filter for AAF Roll-O-Mat is a 65-foot fiberglass replacement roll engineered to drop directly into American Air Filter (AAF) Roll-O-Mat automatic roll filter machines without modification. The roll is wound on a core matching the OEM specification, so it advances correctly through the existing equipment without binding or alignment issues.

Identify your equipment and roll size

Match your existing equipment and current roll to the correct Koch replacement using the reference chart below. Look at the size designation printed on your current roll (e.g., a number like "3 & 33", "4 & 45", "5") and find the matching Koch model number.

What you get: one 65-foot AAF Roll-O-Mat-compatible roll

Each variant on this page is one single roll — not a case or pack. The variant price is the per-roll price. Each roll is 65 feet long, scrim-backed fiberglass media, with the correct core for your equipment. Available sizes for AAF Roll-O-Mat machines:

• OEM size 3 & 33 — Koch model A3GD, core width 32-3/4″
• OEM size 4 & 45 — Koch model A4GD, core width 44-3/4″
• OEM size 5 — Koch model A5GD, core width 56-3/4″
• OEM size 6 — Koch model A6GD, core width 68-3/4″
• OEM size 21 — Koch model A21GD, core width 20-1/4″
• OEM size 22 — Koch model A22GD, core width 22-1/4″
• OEM size 25 — Koch model A25GD, core width 24-7/8″
• OEM size 39 — Koch model A39GD, core width 38-1/2″
• OEM size 40 — Koch model A40GD, core width 39-7/8″

Type GD fiberglass media construction

Type GD is Koch's standard fiberglass automatic roll media:

• Media: High-quality spun glass (fiberglass), progressively dense with adhesive gel
• Length: 65 feet per roll
• Color: Blue tint on the air-entering side (Koch standard for Type GD)
• Backing: Full-width integral scrim backing — protects against necking and fiber break-off as media tensions through the machine
• Initial pressure drop: 0.14″ w.g. at 500 FPM face velocity
• Dust holding capacity: 70 grams
• Arrestance: ~80% per ASHRAE 52.1
• Application: Most commercial and industrial automatic roll machines operating at normal air velocities (around 500 FPM)
• Reference bulletin: Koch K-11586

Core specification for AAF Roll-O-Mat machines

2-1/8″ I.D. fiberboard tube. No drive, discs, or cups. This core configuration matches the original American Air Filter (AAF) Roll-O-Mat machine specification, allowing the roll to feed and tension correctly through the existing drive mechanism.

To insure easy installation, paper leaders and trailers are furnished with each roll — thread the leader through the take-up mechanism the same way you thread the existing roll, and the new media will follow correctly.

When the Type GD for AAF Roll-O-Mat is specified

• Replacement media for existing AAF Roll-O-Mat automatic roll machines — the primary application for this product
• Commercial buildings — office buildings, schools, hotels, retail with installed automatic roll filtration
• Hospitals and healthcare facilities — large air handlers using continuous-feed roll filtration as a primary or pre-filter stage
• Universities and major institutions — building-scale HVAC systems with automatic roll equipment
• Industrial manufacturing — large-volume air handling where continuous-feed filtration eliminates manual filter changeouts during production
• Equipment protection — protects coils, blowers, and downstream filtration in any system using automatic roll equipment

What Type GD captures

Type GD is a standard-efficiency fiberglass media engineered for maximum airflow with reliable dust capture. It captures larger airborne dust, lint, hair, and pollen at face velocities up to 500 FPM, with low pressure drop (0.14″ w.g. initial). Efficiency builds as the media loads — particles caught in the upstream layers help capture finer particles further downstream.

This is an equipment-protection efficiency tier, suited to systems where high airflow and continuous operation matter more than fine-particle capture. For higher-efficiency requirements, consider a multi-stage system with the Type GD as a continuous-feed pre-filter ahead of a higher-MERV final stage.

Other OEM equipment compatibility

Koch produces Type GD fiberglass rolls for the major automatic roll filter equipment manufacturers. Each OEM uses a different core specification, so each replacement is built specifically for its target equipment. Match the roll to your existing machine:

• AAF Roll-O-Mat (this product)
• Air Maze Rollamaze
• Cambridge ElectroAire
• Carrier (31NA-series)
• BLC Industries
• Commercial Filter Fulflo / Mine Safety Roll-Aire
• Continental Conomanuel / Conomatic
• Farr Roll Kleen
• Trane Roll Filter

If your equipment isn't listed above or you aren't sure which Koch part fits, request a quote with the make and model of your roll filter machine and we'll confirm the right part number.

Other Koch automatic roll media options

Koch offers automatic roll media in multiple grades to match different application requirements:

• Type GD (this product): Standard fiberglass spun glass, 65 foot rolls, blue tint. Equipment protection at 500 FPM.
• Type GHD: Premium heavy-duty fiberglass with the highest concentration of glass and adhesive gel. Yellow tint. For extreme conditions or high contaminant loading.
• Type P: 100% polyester synthetic, 65 foot rolls, white. For hospitals and food processing where fiberglass break-off is not permitted.
• Type MD: High-loft polyester with no fiberglass content, 45 foot rolls. Used in hospitals and food plants for the same fiberglass-free reason.
• Type ST: Tackified synthetic, 65 foot rolls. Treated downstream with adhesive for enhanced dust holding. Used in critical-clean-air applications.

Request a quote for any of the alternate media types in the AAF Roll-O-Mat core configuration.

Sizing and ordering notes

• Match the OEM size designation on your current roll to the variant dropdown. The size code is printed on the roll core or end plate of your existing media. The Koch model number (the variant's code) is the actual part number for ordering.
• Confirm core width against the dimensions shown in each variant. The "core width" is the actual width of the media roll — it must match your machine's carriage.
• Sold per roll. Each variant is one 65-foot roll. Order multiple rolls by adjusting the quantity at checkout.
• Need a different OEM equipment compatibility? See the cross-links above for the other eight OEM-specific products in our Koch Type GD line.
• Need a different media type? Type P (synthetic, 65 foot), Type MD (high-loft synthetic, 45 foot), Type ST (tackified synthetic), or Type GHD (premium heavy-duty fiberglass) are also available. Request a quote.
• Replacement guarantee: All Koch Automatic Rolls are guaranteed to meet or exceed OEM specifications. Every roll is subjected to quality control inspection of media and winding technique before shipping.