"We inspect at AQL 2.5" is the most quoted and least understood sentence in Chinese manufacturing. Here is what it actually guarantees.

## AQL is a sampling plan, not a defect allowance

Acceptable Quality Limit (AQL) comes from ISO 2859-1. It defines, for a given batch size, how many units to inspect and how many defects you may find before the batch is rejected.

At AQL 2.5 with a batch of 3,200 units, you inspect 125 pieces. You accept the batch if you find 7 or fewer major defects, and reject at 8. That is not 2.5% of your goods being allowed to be broken — it is a statistical statement about the whole batch, at a defined confidence level.

## The three numbers to put in your PO

1. **Sample size** — normally "general inspection level II", the default in ISO 2859-1.
2. **AQL levels** — usually 2.5 for major defects and 4.0 for minor, with 0 for critical (safety, function, regulatory).
3. **Defect definitions** — what counts as critical, major and minor for *your* product. This is the part most buyers skip, and it is the part that causes arguments.

For an LED flood light: a non-functioning unit is critical. A scratched housing is major. A misaligned label is minor. Write it down before the factory starts production.

## In-line versus pre-shipment

In-line inspection happens while production is running. It catches systematic problems — a wrong component, a drifting measurement — while there is still time to fix them without rework of the whole batch.

Pre-shipment inspection happens when goods are packed, usually 100% packed and at least 80% of the order complete. It confirms what will actually be loaded.

Doing only the pre-shipment check is cheaper but riskier. For a first order with a new factory, we recommend both.

## What a useful report contains

A thumbs-up message is not a report. Insist on:

- Measurements against your specification, with the actual value recorded, not just pass/fail.
- Function tests with the test conditions stated.
- A photo set: carton label, inner packing, product front and back, any defect found.
- The inspector's name and date, and the number of cartons opened.

## The limits of inspection

Inspection is a sample. It cannot find a defect that affects 1 unit in 500 — that is outside the sampling plan's power, and any inspector claiming otherwise is guessing. For high-value or safety-critical goods, add a lab test on the sample: pull strength, dielectric strength, or a material composition check.

## A realistic pass rate

Across the orders we manage, first-attempt pre-shipment pass rate is around 96%. The failures are usually packaging (wrong carton printing, missing manuals) rather than the product itself — another reason to approve artwork and manual copy early, in writing.