I am ordering parts for some MOC I found online. As I compare the parts needed against my inventory, I find that I already have some of them but under different part numbers. For example, I have part 30526 under 53540 in my inventory from the sets we have collected. It gets even more complicated for some parts like this one here and here, under five different numbers.

Is there anyway to retrieve all the parts with alternate numbers?

2 Answers 2


I believe that the part_relationships table in the Rebrickable database can do this for you.

Database diagram

The part_relationships table maps parts to other parts. It tracks relationships such as parts that are prints of other parts, parts that are mold variations of one another, and parts that are alternates for one another. I believe that for your use case, you are interested in mold variations. These are indicated by a M in the rel_type field of the part_relationships table.

You can access the Rebrickable database either using the API or the CSV table dumps. If it saves time, I do maintain a set of scripts to build an SQLite database from the CSV dumps.


What you are asking here is to have all possible part numbers for similarly looking elements. However, while both elements could look to be the same for you they may have significantly different properties.

Both Bricklink and Rebrickable have alternative numbers for the same mould, which is the case with the element in first URL. However, last two items are different elements - one has Thin support and the other comes with Thick support - which is why they are separated. It may be negligible for you, but someone else may find such difference essential.

Another approach would be to lookup by name - searching for "Arm Mechanical, Exo-Force" results in finding both elements, no matter if it is thin or thick version. Looking up by main properties (mainly size) can give you other, alternative elements as well. A good example here would be "Brick 2 x 4" - there is a classic 2x4 brick as well as some modified ones, that would all work fine when building, say a wall. But classic brick may not work if model utilize special properties of that particular modified version of 2x4 brick.

If your issue is with building MOCs that you found on Rebricklable you can adjust your building options. You can apply this permanently across the website in your setting page: Account > Settings > Building Sets/MOCs > Ignore mold variations in parts.

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Or you can apply this setting for particular Set/MOC: Build this MOC > Change Build Options > Ignore mold variations in parts

  • Thanks, especially for the Rebricklable hint. As I am doing all the checking on my own computer using python and CSVs, I hope to have a list of all the alternate numbers of all parts that I have. I am thinking whether such a list exists or not, otherwise this is probably more a question of web scraping and python.
    – Walter
    Jan 4, 2021 at 10:03

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