Trane FLRQB5AH QuikBox Filters: Models, Sizes & Replacement Guide
PRODUCT SPOTLIGHT · OUR BEST-SELLING FILTER SERIES
The FLRQB5AH series is our best-selling filter series at Service First USA. For contractors, property teams and repeat purchasers, the key to a smooth reorder is the complete part number: the shared FLRQB5AH prefix does not mean every size or MERV rating is interchangeable.
This guide brings together all eight FLRQB5AH models currently listed in our catalog.
What is the FLRQB5AH series?
These are replacement media filters for the corresponding Trane QuikBox applications. Trane’s replacement chart identifies four AH size groups, each with MERV 11 and MERV 13 references. The filters are part of a cabinet-and-media system, not a universal replacement for every filter slot. View Trane’s QuikBox specifications and model chart.
All FLRQB5AH models listed at Service First USA
Catalog reviewed November 5, 2026. Each model links to its product listing; consult that page for current stock, package quantity and ordering details.
| Model / product link | MERV | Trane chart dimensions (in.) |
|---|---|---|
| FLRQB5AH18M11 | 11 | 17.8 × 20 × 4.7 |
| FLRQB5AH18M13 | 13 | 17.8 × 20 × 4.7 |
| FLRQB5AH21M11 | 11 | 20.7 × 20 × 4.7 |
| FLRQB5AH23M11 | 11 | 22.7 × 20 × 4.7 |
| FLRQB5AH26M11 | 11 | 25.2 × 20 × 4.7 |
| FLRQB5AH21M13 | 13 | 20.7 × 20 × 4.7 |
| FLRQB5AH23M13 | 13 | 22.7 × 20 × 4.7 |
| FLRQB5AH26M13 | 13 | 25.2 × 20 × 4.7 |
Dimensions above follow Trane’s current website chart. Some manufacturer literature gives the 18-size dimension as 17.75 inches rather than the rounded 17.8 inches. Verify the complete filter number, cabinet label and actual fit before ordering.
MERV 13 two-pack availability
FLRQB5AH21M13, FLRQB5AH23M13 and FLRQB5AH26M13 are now listed in our catalog as two-packs. They are currently out of stock; consult each product page for pricing and contact us for restock timing. A catalog listing does not guarantee immediate availability.
Keep AH, FR and DN part numbers separate
Trane’s chart separates AH, FR and DN replacement references. For example, FLRQB5AH21M11 is listed at 20.7 × 20 × 4.7 inches, while FLRQB5FR21M11 is listed at 20.2 × 26 × 4.7 inches. The shared “21” does not establish the same fit. Copy every letter and number from the confirmed replacement reference.
Choose the specified MERV rating
M11 identifies the MERV 11 version; M13 identifies MERV 13. Match the rating specified for the application. Moving to a higher MERV rating can change airflow resistance, so have your chosen HVAC professional review system requirements before making that change. Read Trane’s MERV and airflow guidance.
Replacement timing depends on operating conditions
“Up to six months” should not become a fixed promise for every building. Trane’s QuikBox installation guide gives estimated replacement intervals for 5-inch media:
- Continuous fan, dusty conditions: 1–2 months.
- Continuous fan, normal conditions: 3 months.
- Auto fan, dusty conditions: 3 months.
- Auto fan, normal conditions: 6 months.
The guide says actual dust loading and airflow can shorten or lengthen those estimates. Follow the documentation for your cabinet and inspect the filter according to the application. Consult Trane’s QuikBox installation and replacement guide.
Make the next reorder easier
Keep a record of the cabinet model, complete filter number, MERV rating, quantity per location and last replacement date. For multiple properties, group orders by exact part number rather than by an approximate size description.
Shop air filters → or send cabinet and filter-label photos through our Parts & Equipment Locator for product-matching support. Air Filters remain publicly priced; check each listing for current details.
About Service First USA: We sell HVAC/R parts and equipment. We do not provide field diagnostics, installation, repairs, maintenance or technician dispatch. Customers arrange on-site work with their chosen contractor.
