Start with the engine and existing ring-set reference

Record the vehicle brand, model and year, the installed engine code, and any piston or ring-set number. Send readable photos of the old packaging and part markings. If an engine or piston has been replaced, state that change. A reliable part reference is useful even when you do not have every measurement.

Separate the bore specification from ring dimensions

State whether the requirement is standard size (STD) or an oversize, using the available label or documented specification. Keep an actual bore measurement distinct from a nominal model description. A ring diameter alone leaves the ring and piston-groove dimensions unresolved.

• Record the known cylinder bore and each ring’s axial thickness, with units.
• Include documented piston-groove widths where available; label each ring position separately.
• Mark whether a value comes from a drawing, a label or a used component. Identify wear or damage in the information supplied.

Describe exactly what one set must contain

List the compression rings and oil-control ring components you require, with the quantity and position of each. Do not infer the number of pieces from the reference photo. If you require a particular construction or material, state it as a requirement and ask for the offered specification to be confirmed.

Put different specifications on separate enquiry lines

Keep standard and oversize requests on separate lines. For each line, add the engine or part reference, known dimensions, set contents, required quantity and destination. Attach a labelled photo or drawing to the matching line. Leave missing information clearly marked as unknown so the supplier response can address it.