ACES and PIES, in plain English.
If you sell auto parts online, you've run into the terms "ACES" and "PIES". They usually come up right before something gets complicated. They sound like jargon built to keep small sellers out. They're not. They're two data standards from the Auto Care Association, and once you see what each one does, the whole picture gets simple.
ACES: The vehicles a part fits
Aftermarket Catalog Exchange Standard. ACES describes fitment. Fitment is which vehicles a part belongs on, down to year, make, model, engine, and sub-model. It answers one question: "what does this part go on?"
PIES: The part itself
Product Information Exchange Standard. PIES describes the product. That covers part numbers, descriptions, attributes, dimensions, weights, and images. It answers a different question: "what is this part?"
The shortcut to remember: PIES is the part's ID card. ACES is the list of cars it belongs to. Used together, they let any marketplace show the right part to the right buyer. That is exactly what eBay is trying to do every time someone shops for a component.
Why eBay can't really sell your part without them.
eBay Motors runs on fitment. When a buyer selects their vehicle and searches, eBay filters the entire catalog down to parts marked compatible with that vehicle. A listing with no fitment data simply isn't in that filtered set.
Surface 01: The compatibility table
That Year/Make/Model grid on a parts listing is fitment data. Fill it in and your listing enters "Shop by Vehicle". That is the way most parts buyers actually search.
Surface 02: The Guaranteed Fit badge
eBay's Guaranteed Fit reassurance is built on accurate compatibility data. No verified fitment, no badge, and no buyer confidence at the point of purchase.
A listing without fitment data isn't ranked low. It's invisible to the way most parts buyers shop.
This is the part sellers underestimate. You can have a competitive price, clean photos, and a fair title. You can still get near-zero views, because the listing never enters the vehicle-filtered results in the first place. Fitment data isn't a nice-to-have field at the bottom of the form. It's the cover charge.
What it costs to get wrong.
Fitment failures show up in two places. Since eBay shifted parts-return shipping onto sellers, the second one now costs real money.
Cause 01: Missing fitment, the silent loss
- The listing is excluded from "Shop by Vehicle" search.
- Impressions, click-through, and conversion all fall well below listings with complete compatibility.
- You never see it as a problem. There is simply no traffic to explain.
Cause 02: Wrong fitment, the expensive loss
- "Universal" and skipped engine codes invite "doesn’t fit" returns.
- eBay made parts returns free. The two-way shipping lands on the seller.
- Bad return reasons accumulate against your seller account.
Wrong fitment is the number-one reason auto parts get returned. Complete, accurate compatibility data is the most direct lever a seller has on return rate. Sellers who add it routinely report fewer "doesn't fit" claims and cleaner account metrics.
You don't need to become a data analyst.
Here's the honest catch: ACES and PIES were designed for manufacturers and large distributors. These are companies with catalog teams whose whole job is maintaining fitment tables. A salvage yard or a three-person eBay shop doesn't have that, and shouldn't need it.
Building ACES applications by hand means mapping every part to every compatible Year/Make/Model/engine combination. That is hundreds of rows for a single common component. It also means keeping it current as vehicle data changes. That's not a listing task. That's a second job.
The practical answer isn't to learn the standards. It's to use a platform that generates standards-aligned fitment for you. GridX Connect's fitment engine cross-references 1.17 billion verified vehicle-to-part relationships, scores every match for confidence, and pushes the result straight to eBay's compatibility table. This happens automatically, on every listing. You list the part; the fitment data is handled.
| Metric | What it means |
|---|---|
1.17B |
Verified relationships. The matching corpus. Engine-precise fitment is only as good as the data behind it. This is the data behind it. |
98% |
First-pass accuracy. Automated, then reviewed. 98% of fitments land automatically; the remaining 2% surface as quick review tasks. |
419 |
eBay categories. Mapped for you. The right eBay Motors category is picked alongside the fitment. There is no manual hunting. |
How fitment data gets onto your listing.
No spreadsheets of Year/Make/Model rows. The flow is three steps, and you only touch the first one.
Step 01: Identify the part
- Start from a part number, a salvage VIN, or a photo.
- GridX resolves it to a verified OEM part and its catalog data.
Step 02: Match engine-precise fitment
- The engine cross-references 1.17 billion verified relationships.
- Matches go down to engine and trim, not just "fits 2019 Camry."
- Every match is confidence-scored.
Step 03: Publish to eBay
- Verified fitment populates eBay’s compatibility table.
- The listing becomes eligible for "Shop by Vehicle" and Guaranteed Fit.
If you have existing eBay listings with no fitment data, you don't need to relist them. The FitX module scans live listings, generates verified fitment for the ones missing it, and pushes the updates. Sales history stays intact.
Ready when you are
Skip the standards. Keep the results.
Verified, ACES-aligned fitment on every listing. First fifty SKUs free.