What is a Hollander interchange number?
If you have spent any time around used auto parts, you have seen “Hollander number” or “interchange number” on listings and wondered what it really means. Here is the plain-English version.
The short answer
A Hollander interchange number is a code that groups together parts that are interchangeable - meaning a part from one vehicle will physically fit and function on another vehicle, even a different make, model, or year. Two cars that share the same interchange number for a given part can use the same part.
The system was created in the 1930s and is now the auto-recycling industry’s de-facto standard for describing fitment. It covers a huge share of vehicles on the road.
Why it exists
Manufacturers reuse parts across models and model years constantly. A headlight, a transmission, or a door might be identical across three model years and two trim levels, even though the part numbers printed on them differ. Without a common code, you would have to memorize every one of those overlaps.
The interchange number collapses all of that into a single identifier: “these parts are the same for this purpose.”
Why it matters to a seller
Two big reasons:
- Reach. When you list a part by its interchange, it can be found by buyers searching for any of the vehicles that share it - not just the exact car it came off. That widens your pool of buyers dramatically.
- Fewer returns. Most used-parts returns are fitment errors. Selling by verified interchange instead of by guesswork means the part actually fits when it arrives.
The catch
Interchange is powerful but not magic. Some parts have variations within an interchange group (a connector style, a sensor, a bracket) that matter. Good sellers treat interchange as the starting point and confirm the details that trip up buyers.
reParta builds fitment into the workflow so each part is listed against the vehicles it actually fits - reaching more buyers while keeping returns down.
Interchange is the language of used parts. Learning to read it is one of the highest- leverage skills in this business.
