I bought a SlimFold Micro Wallet last year. It does a pretty good job of holding some cash, a few cards, and otherwise staying out of the way. The inside of the cash compartment has little wings of the softshell material that create interior pockets for additional cards. The wings also provide access to the two other materials that make up the wallet: foil shields for RFID blocking, and pieces of plastic that provide structure to the wallet. Both of these materials just sit inside the pockets and are easily removed.
The two pieces of plastic are about 85mm x 73mm. At 0.25mm thick, they’re just thick enough to perform their intended purpose, but aren’t all that useful for more nefarious purposes. At the suggestion of a friend, I replaced these two pieces of plastic with shims.
I ordered a set of Super Mica Door Shims from Red Team Tools, which comes with sheets in two thicknesses: 0.35mm and 0.50mm. Using the wallet’s included plastic as a template, I cut out one piece of each thickness and inserted them into the wallet. They make the wallet a little stiffer, which I haven’t found to be either good nor bad. But more importantly, they allow me to open doors similiar to how you might use a credit card. I think it’s a great modification to the SlimFold. As previously suggested, it’s a good travel option.