I wanted a simple yet sturdy holder for my credit cards. And it had to be slim. I printed a few, but none of these fitted my needs. And almost all designs are multiple pieces, which resulted in parts breaking easily.

So I designed my own. it holds up to 8 cards. I printed it in PLA (ebony wood). It is printed upright and in a single piece to increase the strength.

And I added a slim case, printed in ABS, and which holds 5, 6, 7 cards.

So I ended up with a nice set of cases for 5,6,7,8 cards that can be printed in any material.

I updated the design to have a significantly larger space to push the cards out. Updated the photos after the print. Let me know if you would like holders for more cards.

I noticed that the clips had a tendency to break due to the layer structure. So, I rotated the design 90 degrees, and added tree support. 

When printing in PETG, the supports were easy to remove.