Fleetguard · HF Hydraulic · return line
HF6125 filter element: specifications & equivalents
The HF6125 is a Fleetguard return-line hydraulic filter element, sized 128.93 × 179.63 mm OD × length, rated at 33 µm class (TWA 33 µm at β=2 per ISO 16889). Verify against the current manufacturer data sheet before ordering.
Envelope OD × L 128.93 × 179.63 mm
Filtration rating 33 µm nom.
Beta rating TWA 33 µm at β=2 per ISO 16889
Thread 1.00 1/2-16 UN-2B
Line type return
Catalog verified. Parameters extracted from the manufacturer’s electronic
catalog / official interchange document and checked 2026-09-28. Confidence score 0.90.
Specifications and cross-references are taken from the Fleetguard online catalog API. Where both TWA and Beta ratings are published the conventions differ — verify cleanliness targets, collapse rating and seal configuration against the current Fleetguard data sheet before ordering.
Specification table
| Parameter | Value |
|---|---|
| Filter type | return line |
| Filtration rating | 33 µm |
| Rating basis | nominal |
| Beta ratio | TWA 33 µm at β=2 per ISO 16889 |
| Outside diameter OD | 128.93 mm |
| Length | 179.63 mm |
| Thread / connection | 1.00 1/2-16 UN-2B |
| End caps | spin-on baseplate with attached gasket |
| Flow direction | outside-in |
| Integral bypass valve | none (housing/valve-dependent) |
| Manufacturer part no. | HF6125 |
| Source catalog | Cummins Filtration / Fleetguard: Fleetguard online product catalog (fleetguard.com) |
| Last verified | 2026-09-28 |
Sources: Cummins Filtration / Fleetguard — Fleetguard online product catalog (fleetguard.com) — accessed 2026-09-28.
Fleetguard® and all model designations are trademarks of their respective owners, used here for identification only — ElementRef is an independent reference site, not an authorized Fleetguard distributor.
Dimensions & series range
| Outside diameter | 128.93 mm (5.076 in) |
| Overall length | 179.63 mm (7.072 in) |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
|
↔ 51211 page in verification queue | Aftermarket | partial | Fleetguard's online catalog lists 51211 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ 6552507 page in verification queue | UFI | partial | Fleetguard's online catalog lists 6552507 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ HF0612500 page in verification queue | Fleetguard | partial | Fleetguard's online catalog lists HF0612500 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ HF0612500JX page in verification queue | Fleetguard | partial | Fleetguard's online catalog lists HF0612500JX as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ P779589 page in verification queue | Donaldson | partial | Fleetguard's online catalog lists P779589 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ Q751211 page in verification queue | Aftermarket | partial | Fleetguard's online catalog lists Q751211 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
|
↔ S59 page in verification queue | Aftermarket | partial | Fleetguard's online catalog lists S59 as an interchange for HF6125. Envelope cross-reference; verify micron grade, collapse rating and seal configuration before substituting. |
Interchange levels: full catalog-confirmed drop-in · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the HF6125 model number is decoded
- HF6125Fleetguard HF-series hydraulic spin-on filter part number.
- 179.63 mmOverall height.
- 128.93 mmLargest outside diameter.
- 1.00 1/2-16 UN-2BSpin-on mounting thread.
- TWA 33 µm at β=2 per ISO 16889Published efficiency ratings.
Typical equipment & applications
- Construction, agricultural and industrial hydraulic circuits
- Mobile-equipment hydraulic return and pressure lines
Selection pitfalls — read before you substitute
- A return-line element is not a pressure-line element: return cartridges (BN4HC low-collapse) tolerate roughly 20 bar differential, while BH4HC pressure executions are rated to 210 bar. Installing a low-collapse element in a pressure housing can rupture the media on cold-start spikes.
- This element has no integral bypass — opening pressure is set by the housing’s reusable bypass valve. Confirm the valve setting (commonly 3.4 bar) is present before fitting.
- “10 µm nominal” and “12 µm at β1000” can describe the very same media — one is reported at β≥200, the other at β≥1000 per ISO 16889. Compare ratings at the same Beta test point, not just the printed micron number.
- Nitrile (NBR) seals are standard for mineral hydraulic oil but fail early in some phosphate-ester fluids and at sustained high temperature; verify seal compound against the fluid data sheet (fluorocarbon/Viton executions may be required).
- End-cap geometry and the number/position of O-rings block interchange even when OD and length match — visually compare end caps before fitting, especially with aftermarket cartridges.
Frequently asked questions
What are the dimensions of the HF6125 filter element?
The published envelope is 128.93 mm OD × 179.63 mm length (5.076 × 7.072 in). Confirm against the housing drawing before ordering.
What micron rating does HF6125 use?
This element is rated 33 µm (nominal class) — TWA 33 µm at β=2 per ISO 16889. Always compare Beta ratings at the same test point: two brands may print different micron numbers for the same physical grade.
What replaces the HF6125 filter element?
7 partial match(es) requiring parameter review
How do I read the HF6125 part number?
See the designation decoder above: each segment of HF6125 encodes size, line type, filtration grade and media/collapse execution.
Is a same-envelope aftermarket element always a drop-in replacement?
No. Matching OD and length only proves the cartridge fits the bowl. End-cap style, seal compound, micron/Beta rating, collapse pressure and bypass configuration must also match; the table above tags every equivalent as full, partial or verify for exactly this reason.
How often should a hydraulic return-line element be replaced?
Replace at the housing manufacturer’s recommended differential-pressure setting (commonly signalled by a clogging indicator), or on a time-based service interval when no indicator is fitted — never wait for bypass to open continuously, because unfiltered oil then reaches the valves.
Other models in the HF Hydraulic series
All 2621 →Reviewed & verified by the ElementRef engineering desk against Cummins Filtration / Fleetguard on 2026-09-28. Read our editorial & correction policy.