“Inspect at AQL 2.5” is the sentence buyers copy into purchase orders without saying the numbers underneath it. The numbers decide who pays for a bad container, and they are worth understanding before a factory quotes against them. This is the plain version of the most common quality clause in China sourcing.
The standard behind the letters
AQL, acceptable quality limit, is operationalized by ISO 2859-1, the sampling standard most inspection work in China runs on (its US twin is ANSI/ASQ Z1.4). The logic is statistical: you do not inspect a whole lot, you draw a sample sized from the lot size and an inspection level, count the defects found, and accept or reject the lot against thresholds. The default practice buyers should name explicitly in contracts: general inspection level II, normal inspection. Inspection firms treat that as the default when the clause is silent, which is precisely when it gets quietly downgraded later.
Critical, major, minor, and the magic numbers
Defects sort into three classes. Critical: unsafe or banned-legal issues, a broken needle in a garment, a missing ground pin. Major: a defect that makes goods unsaleable or out of contract, wrong color against approved sample, functional failure. Minor: cosmetic issues a retail buyer might still sell through, a loose thread here, a scuff there. The threshold set named by QIMA and HQTS as the common deal for consumer goods: critical 0, major 2.5, minor 4.0. Zero tolerance on safety; limited tolerance on function; looser on cosmetics.
Reading it concretely: a worked example with a 200-piece sample under 0/2.5/4.0 accepts the lot at up to 10 major or 14 minor defects and rejects it past those. Two levers move those numbers: tighten the AQL (1.0 major instead of 2.5) or pay for a reduced-inspection level. The class definitions belong in your spec sheet; the factory should see them before production starts, not at the container.
What an AQL report does not tell you
An AQL inspection is a census of a finished lot: it counts defects that already exist. It cannot tell you whether the goods were made in the factory you approved, whether the components inside match spec, or whether the packing floor is the one from your sample stage. It also arrives at the most expensive moment, after your money is in the machine and before the container is on water, when the only real remedy is sorting, rework or a discount argument.
The upstream layer is verification, and it is cheaper than any rework bill: confirm the company behind the PO is the company on the license (a $129 remote request against the National Enterprise Credit Information Publicity System, written report in 2 business days), then confirm the place runs as claimed with an on-site day at $239, nameplate to packing floor, timestamped photos and a written report the same evening or next morning.
Where a field day slots into the QC calendar
Three moments matter: before the deposit (verify the factory), during production (the 20-30 percent mark, where the packing-area checks catch the problems sampling would reject at the container), and pre-shipment (AQL does its census). An on-site day in the middle window is the one most buyers skip and most needed: it is the only stage where the fix is still cheap. Photos of cartons coming off the line, labeled against approved samples, tell you the defect story before the statistician does.
Writing the clause so it survives first contact
Three lines in the purchase order carry the load: the standard and level (ISO 2859-1, level II normal), the thresholds by class (0/2.5/4.0, or whatever you negotiated), and the definitions (your approved sample plus written spec beats adjectives). Add one line about who pays for a re-inspection after a failed one; if the contract is silent, that fee becomes an argument you are having after the fail, from the weaker side of the table.
- AQL sampling runs on ISO 2859-1 (US twin: ANSI/ASQ Z1.4); name level II normal in the contract, or defaults get negotiated later.
- Defect classes: critical (unsafe, zero tolerance), major (unsaleable), minor (cosmetic); the common deal is 0 / 2.5 / 4.0.
- Worked example: at a 200-piece sample under 0/2.5/4.0, 10 major or 14 minor still pass the lot.
- An AQL report counts finished defects; it cannot prove your goods were made where you approved, or that components match spec.
- The QC calendar: verify before the deposit ($129 + $239), check during production, census at pre-shipment.
Frequently asked questions
What AQL levels should I put in my purchase order?
For general consumer goods the widely published default is critical 0, major 2.5, minor 4.0 under ISO 2859-1, general inspection level II normal. Tighten major to 1.0 for higher-risk categories. Write the class definitions too, anchored to your approved sample, and state who pays for a re-inspection after a fail.
Does an AQL pass mean my supplier is legit?
No, and this is the category error that hurts. An AQL inspection samples one finished lot; it says nothing about whether the company exists as registered, whether the facility was built as claimed, or whether the next lot follows the same line. Legitimacy is the registry layer ($129) plus, before large orders, the physical layer ($239 on-site day).
When is the cheapest moment to catch defects?
At 20-30 percent into production. A pre-shipment AQL fail at the container leaves you only rework, sort or discount. A field visit during production, with photos of cartons against your approved sample, catches the same problem while it is still fixable and still the factory's cost.
