Parts Ecommerce SKU Best Practices

If you run a parts ecommerce website, you’re juggling a lot of product ID data-SKUs, MPNs, ASINs, UPCs, and so on:

  1. You need a manufacturer’s part number (or brand SKU) to place a wholesale order.
  2. You need a GTIN or UPC to track inventory and/or improve your Google Shopping Ads performance.
  3. You may have a second SKU that your distributor/wholesale provider uses to identify a part.
  4. You may have your own internal SKU for your website or internal inventory management.
  5. If dealing with Amazon, you’ve got ASINs floating around somewhere, too.

Fun, right? Lots of numbers that are easy to transpose, confuse, or just generally wonder, “Why in the heck do I need that?”

This article will help parts ecommerce newbs understand what these different numbers are, and offer some suggestions to retailers of all sizes when it comes to dealing with this mess.

Let’s Define All These Damn Numbers

Let’s start with some definitions:

SKU – Stock Keeping Unit: Typically an alphanumeric designation for a specific part that’s created for a retailer’s or manufacturer’s internal use. It can be whatever the SKU “owner” wants it to be. SKUs are not consistent from one manufacturer to the next, retailer to retailer to retailer, etc., which makes them hard to deal with.

UPC – Universal Product Code: A number that identifies a specific product, managed by a registration company called GS1 for a fee. Because UPC numbers are registered, they act as a universal ID that all retailers can use to identify products (at least in theory).

GTIN – Global Trade Identification Number: GTINs are essentially the same as UPCs, only technically a UPC is a GTIN…it’s confusing. GTINs are linked to specific individual products.

EAN – International Article Number: Europe’s version of the UPC, but also technically a GTIN.

MPN – Manufacturer Part Number: This is a manufacturer’s own SKU – manufacturers usually reference their part number when they provide fitment data.

ASIN – Amazon Standard Identification Number: A SKU for Amazon.com, but because Amazon tracks all their SKUs precisely, an ASIN can be a form of unique identification like a GTIN or UPC.

In terms of formatting:

  • GTINs (which includes UPCs and EANs) are always numbers. Most of the time, a GTIN starts with several zeros.
  • MPNs and SKUs can be letters or numbers. SKUs and MPNs can also have dashes and/or spaces.
  • ASINs are always letters and numbers.

Best Practice – Never Trust Anyone Else’s SKU (or MPN)

As mentioned above, SKUs and manufacturer part numbers are a free-for-all. There’s no consistency, and there are dozens of situations where completely different manufacturers will use the exact same SKU for completely different products.

For this reason, many distributors and retailers use their own SKU system rather than try to adhere to a SKU or MPN created by some other entity. This prevents confusion when orders come in, only it does add another number to the data pile.

Can’t We Just Use GTINs To Track Everything?

If you’re thinking, “Why would we bother to create our own unique SKU for every part we sell when we could just use a UPC or GTIN?”, you’re definitely thinking about this problem the right way. Unfortunately:

  • Not every manufacturer invests in GTINs or UPCs. Because these numbers have to be registered with GS1, and because GS1 charges a lot of money for registering them, many manufacturers don’t bother.
  • Some UPCs are recycled. Some manufacturers own “used” UPCs that were registered decades ago by defunct retailers, and have re-used them for new products. Re-use is not allowed by GS1, so these recycled numbers might not have any meaning.
  • GS1 doesn’t give away GTIN data. Believe it or not, the company that has a global monopoly on product identification number registration doesn’t grant free database access to look parts up by GTIN.

GTINs are sort of a necessary evil. They’re hard to get away from because they’re so common and well-supported, but they’re also kind of a racket.

What About Tracking Everything With ASINs?

An ASIN – or Amazon Standard Identification Number – is Amazon’s official SKU for a specific product. However, because Amazon is a behemoth, its ASINs are often used by retailers as a form of UPC. ASINs have a lot of advantages in terms of tracking and lookup, but Amazon doesn’t necessarily have ASINs for every product.

If a product has never been offered on Amazon, it does not have an ASIN. Additionally, Amazon all but requires new products listed on its site to have a GTIN. As a result, if a product has an ASIN, it probably has a GTIN as well.

Best Practice – Make Your Own SKUs

Because SKUs and MPNs aren’t always unique, and GTINs aren’t always available, your company may decide to use its own SKUs. If that’s how your company goes, we have some suggestions:

  1. Come up with rules/guidelines for creating SKUs that you and your staff can reference whenever a new part comes in
  2. Use a mix of letters and numbers
  3. Think about ways to include essential specs in your SKUs, like part brand/manufacturer, part finish, part type, item count, location in the warehouse, and so on.
  4. Try to keep it short enough to remember so that you don’t have to immediately write it down when you see or hear it, assuming you’re manually picking, packing, and shipping

For example, the SKU AFE-SAT-5.4-1283-E could refer to an AFE air intake with a SATin part finish that fits on a 5.4L V8 with the internal stock number of 1283 that’s stored in section “E” of the warehouse.

OR, that SKU could be simplified to AFE-SAT-1283 or just AFE-1283. Whatever makes sense to you.

Some More DIY Part SKU Examples (For Inspiration)

Example SKU: SSTAIL1015

  • Part: Tailpipe
  • Material: Stainless Steel
  • Date Purchased: 10/15

Example SKU: WPSILV60

  • Part: Water Pump
  • Fits Vehicle: Silverado
  • Engine Size: 6.0L

Example SKU: ENG-GM-72

  • Part: Engine
  • Manufacturer: GM
  • Displacement: 7.2L

Fake Example SKU: YUR2SLO

Another Fake Example SKU: OU812

Who says this SKU business can’t be fun? Organizing an auto parts website is a hoot!

SKU Dos And Don’ts

We’re just going to keep going on and on about SKUs until you fall asleep…


  1. Keep it simple, so that you can train new hires to read them quickly.
  2. Keep it short…but not so short that it doesn’t contain helpful info.
  3. Start with letters to make sorting easier.
  4. Use letters and numbers only.
  5. Document the SKUs somewhere important, and make that info available to everyone who works with your inventory.
  6. Document the SKUs in your accounting system.

SKU Dont’s

  1. Don’t re-use SKUs for different parts…if you have a SKU for a part that gets discontinued, that SKU should be discontinued as well.
  2. NEVER use the letter “O”, the letter “i”, the letter “L”, or any other characters that can be easily confused.
  3. Don’t use non-standard characters, like &, ~, ^, $, |, etc. The problem with these characters is that they’re not always easy to say or type into a computer. And, some data systems don’t support them.
  4. Don’t use a SKU that’s so detailed it becomes unwieldy.
  5. Don’t let anyone change your SKU system without good cause. Once you set up a SKU system, changing it can be a lot of work, and it can make historical analysis/records look-up that much harder.
  6. NEVER start SKUs with the number zero. The first time you import data into Excel, there’s a good chance those zeros disappear.

In Summary

Ideally, all auto parts and accessories companies would be following one universal part numbering system that corresponded to a recognized fitment code, but that’s just not the world we live in.

So, if you’re a retailer trying to deal with all this data, you want to:

  • Develop your own SKU system that makes finding parts and fulfilling orders easy.
  • Keep track of MPNs, alternative SKUs, ASINs, and GTINs (which includes EANs and UPCs) for every SKU, as they can be really helpful for ordering, cross-checking, and more.

We often tell our clients that parts ecommerce is a data business, and SKUs are just one aspect of this data. Accounting for product catalog data like SKU, MPN, GTIN, and UPC doesn’t scratch the surface when it comes to fitment, cross-reference, dimensions, variants, and so on, but we’ll leave that for another post.

Have fun!

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