I found this great storage holder for the Terraforming Mars hex tiles but it didn't have a lid.

So I made one! In addition to the lid, I also added in some notches on the base and lid so they lock together tightly.

The holder has 6 slots for the city/greenery tiles, 1 slot for all the specialty tiles, and 1 slot for the 9 ocean tiles and the capital tile.

The lid is a little tight so it takes a little force to get on and fully seat, but it won't accidentally come off which is more important.

Here is also a link to my card boxes specifically for the base game of Terraforming Mars!