If you put about 4 cards in it, or a couple of cards and some cash there is enough pressure inside the wallet to hold everything in and you can turn it upside down and shake it and nothing falls out. I have a gif on my twitter account. This is printed in NinjaFlex and uses about 20 grams of filament. The flexibility allows you to easily retrieve your cards.
I made one for my son and he wanted to be able to put his cash in like you do for a wallet so I made it taller.. cash_wallet