This is tank chain compatible with Lego Technic.
The lego gear can drive this chain.
There is 2 version, one with support and the other without.
With support, the chain axis are more round shape, so this helps running smooth.
After print, this support need to be removed by cutter.
I applied horizontal expansion -0.12mm
You can increase or decrease according to your printer setup.
Removing or adding chain is easy.
To add chain, cut little bit of axis and slide in.