Layers of leather do two things to a wallet. They are added to create pockets but also create thickness. In the end, they are a double whammy regarding wallet bulk as space fills up on top of layers of leather.
Slimmy R1S1 is an ultra-compact minimalist wallet that eliminates excess layers of leather and is perfectly sized for credit cards and your ID. Two side slots for less frequently used cards also create a hold on the center pocket.