Where the gap opens
A requirement written as "nitrile examination gloves, size M, 100 per box" leaves several decisions to somebody else: weight, cuff length, texture, powder status, colour, and the standard the product is tested against. Each of those has a default in a factory, and the default is usually the cheapest option that still matches the words.
The same happens in pharmaceuticals when a salt form is not stated, in laboratory supply when instrument compatibility is assumed, and in consumables when sterility is implied rather than written.
Write the specification as a set of decisions
The most reliable specifications read like a list of resolved questions rather than a product name. If a line item cannot be manufactured incorrectly while still matching the text, it is specified well enough.
- What the product is, in unambiguous terms including form and grade
- What standard or pharmacopoeia reference applies, if any
- Primary packaging, secondary packaging, and the unit of sale
- Labelling: language, required content, and who supplies the artwork
- Shelf life remaining at the point of delivery, not at production
- What is explicitly excluded, where a cheaper variant is common
Confirm in the other direction
A specification that has only travelled one way has not been confirmed. The useful check is to ask the manufacturing side to restate what they will produce, in their own words, and then compare that against the original requirement.
Differences surface immediately in that comparison. Silence, by contrast, is not agreement. It usually means the question was never reached.
Check before it moves
A pre-shipment check against the written specification is inexpensive relative to the cost of a rejected consignment. It should compare physical goods against the specification document, not against a memory of the conversation.
Where a difference is found, the decision belongs to the buyer. Some deviations are acceptable and some are not, and only the buyer knows which is which for their market.