This is a folding wallet made with TPU filament.  

The pockets for cards and ID face inwards toward the fold so they cannot fall out until you fully open the wallet.

I had an earlier version of this that I used for 4-5 years until it finally blew a seam. 

I couldn't find the original model and it had been just a little smaller than I wanted so I built a new one from scratch.

Even decided to fancy it up a bit with an faux alligator skin texture.