This is an film spool adapter to use 120 film in cameras that originally took 116 or 616 type film. Note: this does not mean that the "red window" numbers
...Plus will line up, just that you will be able to load 120 sized spools into the camera.
There are a couple of these already available on Thingiverse, but they didn't quite fit my one of my cameras, so I remade it to fit. They should work in any 116/616 camera.