It is the question we get most often, and it has a short answer: it depends what you play. Yu-Gi-Oh! cards are smaller than Pokémon, Magic, One Piece and Lorcana cards, and sleeves are not interchangeable. If you buy the wrong size the card slides around inside the sleeve, air gets to the corners, and in a tournament the deck is not even legal because the cards are not uniform.
The two sizes that exist
Standard size. Pokémon, Magic: The Gathering, One Piece Card Game, Disney Lorcana and Dragon Ball all use cards of roughly 63.5 × 88.9 mm. The right sleeves are the so-called standard size.
Japanese size (or small size). Yu-Gi-Oh! and Cardfight!! Vanguard use smaller cards, around 59 × 86 mm. You need japanese size sleeves, usually listed as 62 × 89 mm.
A sleeve is always a few millimetres bigger than the card: that is what lets it slide in without scraping the edges and keeps pressure off the corners. That is why looking for a sleeve that matches the card exactly makes no sense.
Which to get, in practice
If you play Yu-Gi-Oh! you need japanese sleeves. The Ultra Pro Matte 60-pack (62 × 89 mm) is the classic choice: matte finish, no glare under shop lighting, and a 60-pack covers exactly one deck. If you would rather keep the colours bright there are the Ultra Pro Gloss, same size but a glossy surface.
If you play Pokémon, Magic or One Piece you need standard size. The Dragon Shield Matte are PVC-free and archival safe, meaning they are designed not to damage the card over time: they are what we recommend if you actually play the deck rather than just store it.
Matte or gloss?
It is not only about looks. Matte sleeves slide better against each other, so the deck shuffles more smoothly, and they do not reflect light: if you play in tournaments or film your games, they are the right call. Gloss sleeves make the artwork pop and look better on a shelf, but they tend to stick together when new.
Are inner sleeves really worth it?
They are if the card is expensive. Inner sleeves go under the normal sleeve, often the other way round, so the card is sealed on both sides and no dust or moisture gets in. Double sleeving protects far better, but it makes the deck thicker: worth checking if your deck box is already full.
And penny sleeves?
Penny sleeves are the thin clear sleeves that cost a few cents each. They are not for playing: they are for storage, for shipping, and for protecting a card before it goes into a toploader. If you open packs regularly, a 100-pack at home is a must.
For the cards you really want to keep safe, the bundle with 25 toploaders and 125 sleeves is the cheapest way to start: penny sleeve as the first layer, rigid toploader on top, and the card will not bend again.
How many should I buy?
For a tournament deck, count the full deck plus a margin: sleeves wear out, the edges get scratched and they need replacing every few months if you play often. Tournament players always keep a spare pack, because a damaged sleeve halfway through an event is a problem: if a card is recognisable from the back, the judge can penalise you.
You will find all the sleeves, toploaders and accessories in the Accessories section.