Two front bumper covers for the same model, same colour, same shape in the photo. Different OE numbers. One fits; the other does not. The difference is rarely visible, which is how a buyer ends up holding dead stock that looked correct at the quoting stage.
Six things separate numbers that look interchangeable. All of them are readable before an order is confirmed.
1. The revision block changes without changing fitment
A Honda number closes with a three-character block such as H51. Honda revises that block when a part changes — material, supplier, a minor dimension — without changing what it fits. A later letter marks a superseded number. The part it replaced was not wrong, only older.
The practical rule: order against the current number, quote against the number the customer gave you. Substituting silently means the customer’s own system no longer matches your invoice, and the discrepancy surfaces at goods-in rather than at order.
Nissan puts that information in the final two characters instead. 00 to 19 usually marks colour and trim differences, 25 to 29 service kits, 40 to 45 a different material, 60 to 69 a service-only variant. A number ending -JK04A and one ending -JK000 can be the same bracket in two specifications, not two brackets.
2. Left and right are separate part numbers
On Honda paired components, the lower part-family number is usually the right-hand side. 33100 is a right headlamp, 33150 the left. 77101 a front bumper, 04711 a front bumper face.
Reading the pair backwards is a routine mistake and an expensive one, because the part arrives correct in every respect except orientation. If a quote does not state the side, ask before confirming rather than inferring it from the description.
3. Primer is not paint
A Honda number ending ZZ is supplied in primer — a grey, unpainted surface. The same component without ZZ may carry a different finish, and trailing letters after the main block often encode the body colour.
Quote the ZZ number against a request for a painted bumper and the customer receives something that still needs painting. The part is not defective; the quote answered a different question.
Mazda handles colour the same way with a trailing suffix: KD45-61-J6X-9U is a cabin filter whose final code identifies the variant.
4. The middle block names the car, not the part
This is the block buyers skip most often. In 45022-TVA-A00, TVA identifies the model the part was first designed for. In Nissan’s 54668-JK04A, the first three digits are the section — suspension in this case — and the second block names the vehicle.
Two consequences follow. A part can legitimately carry one model code and fit several vehicles, because the code records where it started rather than everything it suits. And when the model block does not match the vehicle on the enquiry, the conversation has gone wrong before any money has moved.
Mazda makes this the easiest of the Japanese brands to read: the number opens with the platform. BP4K-34-380 reads as platform BP, suspension group 34, component 380. A number beginning ND cannot belong to a CX-5.
5. Market specification splits one nameplate
A Civic built for Europe, North America and Japan differs in lighting, emissions hardware, suspension and restraint systems. Running changes mid-cycle are frequent enough that build date decides more often than model year does.
That request exists because the VIN is the only dependable route to a factory build. On Japanese-market cars there is no 17-character VIN at all — there is a chassis number such as CL7-1234567, which a field expecting a VIN will reject outright.
If you are checking fitment for an import, the chassis number is the identifier that reaches factory data. Send that, not a registration document number issued in the destination country.
6. Packaging and origin are not the part
The same OE number arrives in a dealer box, a bulk pack, or a supplier’s own carton. Packaging sits outside the part number. What the number identifies is the component itself. A fifteen percent gap between two quotes for one number is usually packaging, origin or freight terms rather than a discount on the same goods.
Confirm what the price covers before comparing it with anything.
What to check before confirming a line
- Part-family block matches the description you were given, not just the brand
- Model block is plausible for the vehicle on the enquiry
- Side is stated explicitly, not inferred
- Finish is stated — primer, painted, or colour-coded
- Revision letter is current, and the customer’s original number is recorded on the quote
- Packaging and origin are stated if the price is being compared against another quote
All of it works without a catalogue subscription — you need the number in front of you, and the habit of reading three blocks separately rather than treating the whole string as one opaque key.
If you want to check what a number is listed against before you commit, our parts by vehicle model index shows which models each part is recorded for, with the OE number and replacement references on every part page.