How to Find Your Part Number (MPN)

Key takeaways

The part number (MPN) is the manufacturer's own code for one exact product. Match that, not the product name.
Look on the nameplate or rating plate first, then on the original packaging label.
Copy every character, including the suffix and the series letter. A different ending can mean a different product.
No readable label? Send us photos of the part and of the machine it came from.

Every part we list is identified by its manufacturer part number. If you have that number, finding the right replacement is usually a single search. If you don’t, this guide shows where to look and what to do when the label is missing.

Part number, model number, serial number

These three numbers are often printed side by side, and they do different jobs.

Part number (MPN). The code a manufacturer gives to one specific product among everything it makes. Manufacturers call it different things: Siemens uses article number, Rockwell Automation (Allen-Bradley) uses catalog number, and you will also see order number, P/N or Ref. This is the number to match.
Model or product name. The name of a product line or system, such as a drive family or a laser platform. Several different parts can belong to the same model, so the name alone is not enough to order by.
Serial number. Identifies one individual unit. It tells the manufacturer when and where that unit was made, but it does not tell you which product to buy. Keep it anyway: it helps when you ask us or the manufacturer to identify a part.

Where to look on the part

The nameplate or rating plate. Most industrial parts carry a printed plate or sticker on the housing. On Rockwell Automation ControlLogix modules, for example, the nameplate with the catalog number and series letter is on the right side of the module. On some units the plate sits behind a cover or on the side of the heat sink, so check every face.
The packaging label. If you still have the original box, the same number is usually printed on the carton label. Siemens states that the article number appears both on the product and on its packaging label.
A QR or data-matrix code. Newer parts often carry one next to the label. Siemens products with an ID Link code open a digital type plate when you scan them, and Rockwell Automation suggests scanning the QR code on the product label for product-specific information.
The machine’s documentation. If the part came out of a larger machine, its spare-parts list or service manual often names the part number for each position.

Copy it exactly — suffixes and series matter

Part numbers are precise. The last few characters often decide which version you have, so write down the whole string as printed, including dashes and the letters at the end.

Suffixes. Siemens gives products with new, incompatible functions a new article number. Two numbers that differ only in their last characters can therefore be two different products.
Series letters. Rockwell Automation prints the product series on the label after SER, for example SER B. The series is tracked separately from the catalog number, and some manufacturer notices apply only to particular catalog-and-series combinations. Note it next to the part number.
Look-alike characters. Check O against 0, I against 1 and B against 8, especially on worn or small print.

Then search our store by that number. Every listing shows the brand and the manufacturer part number. If nothing comes up, try the number without dashes or spaces, or with fewer characters at the end.

When the label is missing or unreadable

Labels fade, peel off or get painted over. You can still often identify a part from what is left. Send us, through the Request a Part form:

a photo of whatever remains of the label, even if only part of it is readable
photos of the part from every side, including connectors and any markings on the board or housing
the brand, model and serial number of the machine the part came from
where in the machine it was fitted, if you know

We will check what we have and tell you if we cannot match it.

Before you order

Compare the part number on the listing with yours, character by character. Where the listing photos show the label, compare that too.
Check the condition label and what it means for returns and warranty — see our Condition Guide.
If anything does not match, or you are not sure, ask us before you order.

Frequently asked questions

Is the part number the same as the model number?

Not usually. The model number names a product line or system; the part number identifies one exact item. Order by the part number.

What does MPN mean?

Manufacturer Part Number: the code the manufacturer assigns to one specific product among all the products it makes. It is the number shown on every listing in our store.

My part number matches except for the last letter. Is it the same part?

Treat it as a different part until it is confirmed. Suffixes and series letters often mark a different version. Send us both numbers and we will check.

Where is the part number on an Allen-Bradley module?

On the nameplate. On ControlLogix modules it is on the right side of the module, together with the series letter (shown after SER) and the manufacturing date. New, unopened parts also carry it on the carton label.

Where is the article number on a Siemens part?

Siemens prints the article number on the product itself and on the packaging label. Newer products may also carry an ID Link QR code that opens a digital type plate.

I can't find any label. Can you still help?

Often, yes. Send photos of the part and the details of the machine it came from through the Request a Part form, and we will check what we have.

How to find your part number