Flexible Pouch Wallet
This is a low-profile flexible pouch style wallet with convenient access slots, allowing you to slide a single card off of the stack of cards inside at a time with a flick of your thumb. The wallet is concave along most of its length, squeezing the stack of cards inside firmly to keep them from falling out. At the mouth, the wallet is convex, allowing you to squish it at the edges to open it and reach inside for a particular card. It can fit up to 8 standard plastic cards and a few folded bills at the same time.
Two STL files are included, one with my username watermark, and the other without.
UPDATE: I have been using this wallet daily for 10 months now, with no visible wear or tear. See last 3 photos for its current state.