This is a case to protect LDS pocket-size scripture sets: https://store.churchofjesuschrist.org/pocket-size-scripture-set/5638680482.p?style=English&color=Pocket

The goal was to make it loose enough to insert and remove them without damage, but snug enough that they don't slip out. I have tested on several sets and they fit well, but you may need to scale up by 1–2% if it's too tight.