ANKOM Filter Bag Alternatives: FB25 for F57, GB3 for XT4
Looking for an ANKOM F57 or XT4 filter bag alternative? FB25 and GB3 are direct replacements that run in ANKOM bag-method instruments without modification — with free trial kits to validate before you switch.
Published 2026-10-22 · Sonnen application engineering team, October 2026. ANKOM, F57 and XT4 are trademarks of ANKOM Technology Corp.; Sonnen is not affiliated with, sponsored or endorsed by ANKOM Technology Corp. Compatibility statements refer to dimensional fit and method workflow only.
In short: if your lab runs ANKOM bag-method fiber or fat instruments, two SONNEN consumables are dimensioned as direct replacements — the FB25 (25 μm hydrophilic) replaces the ANKOM F57 fiber bag, and the GB3 (3 μm hydrophobic) replaces the ANKOM XT4 fat-extraction bag. Both run in ANKOM instruments without modification, and we ship free trial kits so you can validate recovery and precision on your own samples before changing anything in your supply chain.
Compatibility at a glance
| ANKOM consumable | SONNEN replacement | Application | Instrument modification |
|---|---|---|---|
| F57 fiber filter bags | FB25 — 25 μm, hydrophilic | Crude fiber, ADF, NDF and dietary fiber determination by the filter-bag method | None — same racks, same workflow |
| XT4 fat-extraction filter bags | GB3 — 3 μm, hydrophobic | Solvent-based crude fat extraction by the filter-bag method | None — same racks, same workflow |
What stays the same when you switch
The filter-bag method is defined by the bag geometry and pore size, not by the brand on the box. Sample mass, digestion and extraction programs, rinsing cycles and calculation formulas all stay unchanged — the FB25 and GB3 drop into the existing ANKOM workflow, so there is no method revalidation beyond your own verification runs.
Why labs evaluate an alternative supplier
Filter bags are consumed on every single test, so supply continuity and unit cost matter as much as the instrument itself. Evaluation users report results comparable to imported filter bags at roughly half the cost, and the bags are already in recurring volume use by major feed groups in China. We state this as user-reported experience, not as a lab-certified equivalence claim — which is exactly why the trial kit exists.
How to validate before you switch
- Request a free GB3/FB25 trial kit through the contact form — choose the “Free filter-bag trial” option.
- Run your routine reference samples in parallel: your current bags vs the trial bags, same instrument, same program.
- Compare recovery and repeatability on your own matrices — your acceptance criterion, your call.
- If the results hold, move to a standing order; if they don’t, the trial cost you nothing.
Honest limitations
We make no claim beyond dimensional compatibility and user-reported comparability. Filter-bag performance can vary with sample matrix and fat/fiber fraction, so parallel validation on your own samples is a hard requirement, not a formality. And if your instrument is under an ANKOM service contract, check its consumables terms before switching.
Questions buyers ask us.
Do FB25 bags really fit ANKOM F57 applications?
Yes — the FB25 is dimensioned as a direct replacement for the ANKOM F57 fiber filter bag and runs in ANKOM bag-method fiber analyzers without modification. Pore size is 25 μm, matching the fiber-method requirement. We still recommend validating on your own samples with a free trial kit before switching supply.
What about ANKOM XT4 fat-extraction bags?
The GB3 (3 μm hydrophobic) is the direct replacement for ANKOM XT4 bags in solvent fat extraction — same workflow, no modification. The same trial-kit validation path applies.
How much can we save on filter bags?
Evaluation users report results comparable to imported bags at roughly half the cost. Your actual saving depends on volume and shipping terms — request a quotation with your annual consumption for an exact figure.
Need this method on your samples?
Tell us your sample type and the standard you work to.