Even if you put a single paper-thin card inside, it will still sit tight and won't fall out. No, not because the brand-new case is freshly tight, but because there's a tension clip located inside towards the bottom.
That means you do not have to worry about stretching the case from inserting too many cards because even if it stretches, the tension clip will still do its job of trapping the cards.
I've included a diagram of the case shown sideways with the tension clip inside:
That means you do not have to worry about stretching the case from inserting too many cards because even if it stretches, the tension clip will still do its job of trapping the cards.
I've included a diagram of the case shown sideways with the tension clip inside:
