Start with the size, but do not stop there
A size marking such as 27 × 41 × 8.5 is a useful starting point when sourcing a replacement power steering oil seal. It helps narrow the search, but it does not establish that every seal carrying those dimensions will work in the same steering assembly.
For buyers and steering-system rebuilders, the practical goal is to match the original sealing arrangement—not simply find a ring that looks similar.
1. Confirm what the dimensions describe
Record the complete size marking, including decimals, slashes and any additional height values. Confirm the units and dimension order against the supplier's drawing rather than assuming that every catalog uses the same convention.
Keep the original marking alongside your measurements. A worn or distorted sample should not be the only basis for selecting a replacement.
2. Compare the seal profile and its working position
Photograph both faces and the side of the original seal. Note visible lips, springs, support elements and the outer surface, without assuming that an external resemblance proves the internal construction is identical.
Also identify where the seal operates. Rotary and reciprocating sealing arrangements have different requirements. A dimensional match does not, by itself, establish suitability for a different type of motion. See Trelleborg's rotary seal guidance.
3. Match material and operating requirements
Check the specified material, the fluid being sealed and the assembly's operating requirements. Do not assign a pressure or temperature rating from size, color or a material abbreviation alone.
Seal selection depends on the design and operating conditions, including pressure, temperature and motion. SKF's guidance likewise treats design and material selection as application-dependent, not a universal size-based rule. See SKF's seal-selection overview.
4. Use reference numbers as cross-checks
Record the steering assembly number, original seal markings and supplier references separately. Explain which number came from the original part and which came from a replacement catalog.
For a practical sourcing example, the KOKI K-00265 27 × 41 × 8.5 power steering seal is currently listed with type CNB1W11/7V1, material NBR, and references BP4705I, RK-OS4112, BP4705H and BP4705E.
These listing details help identify the product for an inquiry. They do not establish universal interchangeability, a vehicle fitment or an operating limit. Ask the supplier to verify the candidate against the original assembly information and sample.
5. Send a complete matching inquiry
Before requesting a quotation, prepare:
- The complete size marking and any drawing available.
- Clear front, rear and side photographs of the original seal.
- All readable part, assembly and reference numbers.
- The seal's installation position and known material requirement.
- Vehicle or steering-unit identification, where available.
- The quantity required.
A useful inquiry might read:
Please help identify a replacement for this 27 × 41 × 8.5 steering seal. The original markings and assembly details are attached, together with photographs of both faces and the side. Please confirm the suitable profile, material and reference before quoting.
The takeaway
Use dimensions to find candidates, then check the profile, material, reference information and application before ordering. For this example, view the existing K-00265 product page or send KOKI your sample details for matching.