Product specification sheet: template for China factories
A usable product specification sheet gives every requirement a measurable limit, a checking method and the evidence that proves it, all under one document number and revision. For a moulded enclosure, replace ‘fits our electronics’ with an assembly drawing, a datum and a fit test. The same revision then goes to every factory and to the inspector.
The fields every specification sheet needs
Head the sheet with the product name, a document number, the revision and date, the owner, and a list of every attachment that belongs to that revision: drawings, material schedule, artwork, packaging files and test instructions. Then fill one row per requirement using the fields below. The rows are suggested fields, not universal product standards; set the limits from your design and intended use.
Where you have not decided something, write ‘open: supplier proposal required’ rather than leaving it blank. A blank lets each factory choose silently, and you will be comparing different products.
| Requirement | What to write | How it is checked |
|---|---|---|
| Fit and dimensions | Drawing revision, measurement datum, critical dimensions and tolerances; the mating parts | Measure from the stated datum and assemble with the named mating parts |
| Material and components | Material grade, approved component references, and that substitutions need written approval | Check material records and component identification; add testing where needed |
| Appearance | Retained reference sample, viewing conditions, photographs of acceptable and unacceptable features | Compare under the agreed conditions and record borderline findings |
| Function | Operating conditions, test sequence, duration and pass or fail criteria | Run the written procedure and keep results against the batch identifier |
| Labelling and marking | Approved artwork file, barcode, required markings and their position | Compare with approved artwork and scan barcodes |
| Packing | Contents list, carton arrangement and protection of vulnerable features | Unpack and reconcile contents; check the agreed transport test |
| Documents | Required reports, drawings, instructions and declarations | Match documents to the ordered model and revision |
Write limits, not adjectives
Words such as ‘high quality’, ‘strong’ and ‘same as sample’ cannot be inspected. Turn each one into a limit and a method: ‘strong’ becomes a load, a duration and what counts as failure; ‘same colour as sample’ becomes a retained reference, a light source and the photographs that show the limit; ‘good finish’ becomes a defect list with photographs.
Hypothetical worked example: the buyer of a moulded electronics enclosure specifies mounting-hole centres of 80.0 ± 0.2 mm. The acceptable range is therefore 79.8 to 80.2 mm, and a part measuring 80.3 mm fails even if it looks like the approved photograph. These are illustrative design values, not an industry tolerance.
The same row must also say where the measurement starts (the datum), whether it is taken before or after finishing, and which circuit board, connector and lid are used for the fit test. Without the datum, two people can measure the same part and both be right.
Defect classes the inspector can apply
Group defects by their consequence, not by how they look. For the enclosure: a part that will not assemble or exposes a sharp edge is critical; damage that affects use, such as a cracked screw boss, is major; a mark on a non-visible face is minor. Give each class a checking method and an agreed disposition: reject, rework or accept with a record.
If you will use acceptance sampling, the specification should name the standard and edition, the inspection level and the limit for each class. How to read those numbers is covered in AQL sampling in practice; the specification only has to make sure the inspector and the factory are counting the same thing.
Change control: the clause factories skip
Require written approval before any change to material, components, tooling, artwork or a test method, and say so on the sheet. Each change record should name the affected revision and batches, any new sample or test evidence needed, and who authorises production to resume.
Link the approved sample to the revision: give it an identifier, keep a retained counterpart, and record what it approves (appearance, assembly, performance or a combination). If the sample and the drawing disagree, settle which governs each feature in writing before production.
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Common mistakes, and where a specification stops
Writing a marketing description instead of limits; a tolerance with no datum; no revision number, so the factory works from an old file; a sample and a drawing that contradict each other; and translated drawings nobody checked, which our guide to approving translated factory drawings covers.
The specification says what the product is. Pricing terms belong in the enquiry, set out in how to write an RFQ email, and the destination test list comes from your compliance adviser, as in briefing a factory on destination tests. Cambridge China Bridge's product development service can help turn a specification into a controlled production handover.
Related help: sea vs air freight calculator.
Frequently asked questions
What should a product specification sheet include?
A header with document number and revision, then one row per requirement covering fit and dimensions, materials and components, appearance, function, labelling, packing and documents, each with a limit, a checking method and the evidence.
Can I write a specification before the design is complete?
Yes. Mark undecided items as open and ask for proposals or separately priced alternatives, so every factory works to the same assumptions.
Does an approved sample replace the drawing?
No. Use the sample for the features you explicitly approve, and the drawing and test instructions for measurable requirements. State which governs each feature.
What if a factory proposes an equivalent material?
Ask it to name the proposed grade and explain the change, assess fit, function and compliance evidence, and record the decision in a new revision rather than a chat message.