There is one rule that explains most failed China orders: anything you do not specify, the factory decides — in its own favour, and legally. Not out of malice. A Chinese plant works to a document, and where the document is silent it defaults to the cheapest option that still matches what was written. This article is for companies ordering custom or branded goods in commercial volumes — from about 500 units — and covers what a production specification must contain before it goes out for quotation.
Why "make it like the photo" is not a specification
A photo carries shape and nothing else. It does not carry the polymer grade, the steel thickness, the coating microns, the screw standard, the fabric density or the tolerance. Send a photo and you will get something that looks like the photo and costs the factory as little as possible to produce. That is the mechanism behind the most common complaint in the industry — the sample was fine and the batch was defective. The spec sheet is the first stage of the whole process for exactly this reason, as set out in how manufacturing in China actually works.
What a specification must contain
- Identification. Product name, your internal SKU, drawing number, revision number and date.
- Materials, by grade. Not "stainless steel" — 304 or 316. Not "plastic" — ABS, PP or PC with a named grade. Not "aluminium" — 6061-T6.
- Dimensions with tolerances. Every critical dimension, with the permitted deviation. A number without a tolerance is a wish.
- Weight, net and gross, with permitted deviation.
- Finish and colour. Coating type and thickness in microns, plating, anodising, Pantone reference, gloss level, texture.
- Bill of materials for components. Motors, cells, bearings, electronics, fasteners — brand and model where it matters, or an explicit "no substitution without written approval."
- Functional tests. What the product must survive and to which standard: load, cycles, hours, IP rating, voltage, drop.
- Standards and certification. GB, ASTM, EN, IEC — plus whatever your market requires for sale.
- Packaging and labelling. Retail box, inner and master carton, barcodes, shipping marks. Details in packaging development in China.
- Acceptance criteria. Sampling standard and defect limits, plus the reference sample the batch is measured against.
Materials: where substitution hides
Material is the easiest place to save money invisibly, and the hardest for you to detect from a photo report. Name the grade, name the standard the grade is defined by, and require documentary proof — mill certificates, material declarations, or test reports for the specific batch, not a generic PDF from a previous year. For metals this is exactly the role of the mill test certificate, and the same logic applies to polymers, coatings and cells.
Never accept "same quality" or "equivalent material" as an answer. Either it is the grade you specified, or it is a different product with a different price, and you should be told which.
Tolerances: the difference between engineering and hoping
Every dimension drifts in production. Specify how much drift is acceptable on each critical dimension, and say explicitly which dimensions are critical — a factory that must hold every dimension tightly will price the job as if all of them matter, and you will pay for precision you do not need. Tolerances are also the first thing a factory will ask to relax at the design-for-manufacturing stage; that conversation is far easier when the critical few are already marked.
Acceptance criteria in the factory's language
"Good quality" is not an acceptance criterion. A workable one names the sampling standard, the inspection level, and the acceptable number of minor, major and critical defects per lot — then defines, in plain terms and photographs, what counts as each. Without it, an inspector has no authority to reject anything, and the pre-shipment inspection becomes a photo session. How the inspection types work is in quality control when importing from China.
Language, units and format
- Bilingual. English plus Chinese for the operative parts. The person at the machine does not read English.
- Metric. Millimetres and grams, not inches, unless the drawing is dimensioned in both.
- Drawings in two formats. PDF for reading, STEP or DWG for manufacturing.
- Version control. Every revision numbered and dated; the contract references the exact revision.
- Signed by both sides, and attached to the contract as an annex — see what a contract with a Chinese factory must contain.
What not to specify
Over-specification costs real money. Do not demand tight tolerances on non-functional dimensions, cosmetic perfection on surfaces nobody sees, or a premium material grade where a standard one performs identically. Every unnecessary requirement raises the unit price and gives the factory an argument that your terms were unrealistic. Specify tightly where failure matters, loosely everywhere else, and say which is which.
Checklist before you send it out for quotation
- Could a factory that has never spoken to you build the product from this document alone?
- Does every critical dimension carry a tolerance?
- Is every material named by grade and standard, with proof required?
- Are the functional tests measurable, with pass/fail thresholds?
- Are packaging, labelling and barcodes included?
- Are the acceptance criteria and the reference sample defined?
- Is there a revision number, and is it the one named in the contract?
A specification is not paperwork before the real work starts. It is the product, written down. Everything the document does not say, someone in a factory 8,000 km away will decide for you — usually on the day the line starts running.
Writing the spec with the factory in mind
We write and translate production specifications for clients, quote them across several verified factories, and hold the batch against the document with in-line and pre-shipment inspections. Seven years, 3,500+ deliveries and 340+ verified suppliers of doing exactly this — examples in our case studies.
Start with product sourcing or a standalone quality inspection if production is already running.
