This credit card holder is made from 2 parts. It can hold up to 7 cards comfortably but I have fitted 8 although it does get tight.
You need to print the body part and one of the lid designs I made. Feel free to modify the standard part and make your own design. No other parts are needed.
The lid will need to be bent to fit around the body, but once it clicks it should fit perfectly.
Initially the lid may be difficult to open as the nubs that hold the lid closed need to be ground down. This will happen over time or you can manually grind them down to your liking.
Printables: https://www.printables.com/de/model/823182-credit-card-wallet
Thangs: