These are inserts for the Stanley 10-Compartment Deep Pro Small Parts Organizer. My son uses this to transport his Magic The Gathering decks when he goes to play. The Stanley organizer comes with two double wide bins by default. Printing four of these allows you to replace those double bins so the organizer can now carry 14 decks nicely separated. Plus you can print them in different colors to differentiate the decks.

If you would like to make your own modifications I have linked the Onshape file, and have also included a Step File (one with and without the thumb cutout).

Onshape: https://cad.onshape.com/documents/214f1f40e0569c2f12e715bf/w/04f7b3c4f6f20672e6dafb4b/e/9f2ea33e8fb227602580cf5b?renderMode=0&uiState=6582dc066d0cc1027f56e5d8

I hope you find this useful, or can modify things for yourself to fit your use case.