Origami Tyvek Wallets and their credit card pockets.
The Mighty Wallets origami design works in combination with the creases in the Tyvek® material and tension in the folds to allow the wallet to expandable with use.
It is important to consideration that the folding works best when the Mighty Wallet is used at a consistent size. For example if you were to fill a pocket and remove many of the cards in the pocket it might be less tight than it was initially since the folding is less tight after being stuffed.
Given the unique origami design I can understand that the Mighty Wallet is not for everyone but thousands of Mighty Wallet fans have grown to love the simplicity, functionality and long term durability of the Mighty Wallet.
However if you want to try the Stitched Tyvek Billfolds that is a more traditional mechanism.