These index cards were made to sort player cards from the LOTR LCG card game. They will fit in the card tray from Brahm: https://www.thingiverse.com/thing:680004
Btw thanx Brahm for the card tray design :)
Please note that this was made for unsleeved cards.
Please also note that it is not possible to read the index cards when the cards are in (see picture). I could have made them higher but then they would not fit in the core box, which would be worse imo...