Very thin KMC sleeves with vertical insertion. They're the exact same size as a card, allowing to double-sleeve your cards.
Sleeves - Magic: the Gathering
Funko
With its 0.05mm thinness, this is suitable as an inner sleeeve for small-sized trading cards.
KMC Perfect Size Inner Sleeves €“ Mini Size 100 Sleeves Per Pack - 2 Packs
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