I was printing number of connectors for IKEA trains and Brio, they were either too tight or too loose. So I created a customizable version. Just use callipers to measure your connector or holes.
I included a preset (connector.json) for IKEA Lillabo train set.
Printer:
Ender 3 V2
Rafts:
Doesn't Matter
Supports:
No
Resolution:
0.2mm
Infill:
20%
Notes:
Full version with 20% infill is a bit faster to print than the Hollow version and so far I think it's more durable.