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
I create these designs to encourage people to try out flexible filaments or get some new interesting colors of flexibles. For info on purchasing samples of 6 different types of flexible filament go to flexyfilament.com
We developed a great way to distribute cost effective quantities of flexible filament: Splash Spools. A generous amount of filament on a spool with a case so it's not flopping all over the place. Splash Spools store easily in a desk drawer, stacked space or even hang on a wall. Available on www.flexyfilament.com and Amazon. We stock NinjaFlex, Cheetah, SemiFlex, SainSmart, Fillamentum, nGen FLEX, FilaFlex and Flexy.