It is going to sound crazy that I am so excited about this tiny little "ID Insert", but it is literally exactly what I needed and there is nothing else like it out there. Everyday I need to have just 2 cards with me that are accessible - my id badge for the building I work in, and my transit card for the train. I keep them both in my back pocket, and just needed something to put them in to hold them together. I use the clear side for the transit card because the train station scanner is a little more finicky than the building I work in where the ID doesn't need to be visible to scan. This is perfect.
ProsNo larger than the cards themselves, adds no bulk whatsoever.