How to write a product specification sheet

Almost every quality dispute with a Chinese supplier comes down to the same thing: you assumed something they never agreed to. You thought the zips would be metal, they used plastic. You expected a 2mm wall, they poured 1.4mm. Neither side lied. There was simply no written standard, so the factory built to the cheapest reading of a vague brief. A product specification sheet closes that gap before it opens.

Why the spec sheet matters

The spec sheet is the single document that your sample, your inspection, and any future complaint all get measured against. Without it, "this is not what I ordered" is just your word against the supplier's, and you have already paid a deposit.

With a written spec, the conversation changes. The inspector checks the goods against your sheet, not against a feeling. A defect becomes a measurable deviation from a number you both agreed, which is exactly what makes it enforceable.

A factory will always build to the spec you wrote, not the product you imagined. The cost of being vague is paid in the cartons that arrive in Lagos.

What to include

A usable spec sheet covers the boring details that turn into expensive surprises:

• Exact dimensions with units, for every part that matters. Not "medium size".
• Materials and grades. Type of steel, plastic resin, fabric composition and weight in GSM, leather versus PU. Name the grade, not just the family.
• Colours by a reference your supplier can match, such as a Pantone code or a physical swatch you have sent. "Royal blue" means ten different blues.
• Weight of the finished unit, with a tolerance.
• Functional requirements. What it must do, how long, under what load. For electronics, the voltage, plug type and certification you need.
• Labelling and markings. Your logo, care labels, country of origin, barcodes, language.
• Packaging. Inner box, master carton, units per carton, carton markings, drop-test expectations.
• Accessories and what is in the box. Cables, manuals, spare parts, warranty cards.

Photos and drawings are part of the spec

Words alone leave room for interpretation. Pair them with images:

1. Photograph your approved physical sample from several angles, including the parts you care about most.
2. Annotate the photos with arrows and measurements so there is no doubt which dimension you mean.
3. For anything machined or moulded, a simple dimensioned drawing beats a paragraph of description.
4. Keep one sealed reference sample yourself and have the supplier keep an identical one, so both sides can point to the same physical object later. This is the basis of the golden sample process.

Set tolerances, not just targets

Nothing is manufactured to a perfect number, so state the range you will accept. A tolerance says "this dimension should be 50mm, and anything from 49.5 to 50.5 passes". Without one, you are either rejecting goods over a rounding error or accepting parts that drift far from spec.

Set tighter tolerances where they matter for fit, function or safety, and looser ones where a small variation is invisible to your customer. This same thinking feeds directly into your AQL sampling levels, where you decide how many out-of-tolerance units a batch may contain and still pass.

Make the spec part of the deal

A spec sheet that lives only in your email is worth little. Attach it to your purchase contract and reference it by name and version, so the agreed standard is the one the inspector and any dispute will rely on. The mechanics of doing that sit in our guide to a purchase contract with a Chinese supplier.

Get the spec right and the rest of your quality control has something solid to stand on. When your sample is approved against a clear sheet and your terms are agreed, you can make a request to settle the deposit in RMB on Alipay from Naira, knowing both sides are building to the same page.