Sleeve

A sleeve is a plastic protective cover for cards, that prevents scuffing. They can be sold in clear versions or with or opaque backs, in a range of colors, and can even have artwork on their backs. According to Wizards of the Coast, 90% of cards in constructed tournaments are sleeved.

Opaque sleeves
Opaque sleeves provide an advantage, they make older and newer card backs be indistinguishable and conceal minor damage of cards (which would otherwise be unplayable as they are considered to be marked). There are two conditions under which opaque sleeves must be used regardless of a card's condition:


 * If a deck contains both Alpha and non-Alpha cards.
 * If a deck contains double-faced cards and/or meld cards, and the "checklist cards" are not used.

Double-sleeving
While single sleeving protects against general wear and tear, double sleeving makes your cards waterproof and nigh-indestructible. For this, two sleeves are used with the opening on opposite sides. Double sleeving also protects cards from dirt specks, which can be a major problem if any happen to find their way inside of a single-sleeve. Double sleeving is also better for foils since it reduces the air flow around the card and helps prevent warping. Once you push the air out, shuffling is thought to be easier as well.

Rules
Playing with sleeves with artwork is permitted in all DCI official events, including all Premier Events. The Magic Tournament Rules also have parts regulating the permitted specification of artwork sleeves in non-regular REL events (which should have solid borders and had low reflection rate), and also giving Head Judge rights to disallow any sleeves which they decide as unsuitable for the event (for example, sleeves with scratches that make it possible to tell individual cards apart).

During the Booster Draft portion of Professional REL events (Grand Prix main events, Pro Tours, and the World Championship), determined by the number (or lacking of) and opening frequency of double-faced cards of the set(s) used, Wizards of the Coast may announce the event is a pre-sleeved event (i.e. all cards will be pre-sleeved by staff before players "open the packs"); players may replace the provided sleeves with their own sleeves in matches once pool registration is finished in such events.

Manufacturers
Ultra Pro, the Japanese KMC, and Dragon Shield are the main sleeve producers. Ultra Pro also introduced sleeves for oversized cards.

MTG Arena
In MTG Arena, card sleeves are optional cosmetic treatments that change the way the back of a card looks. Once a card sleeve is acquired, you can apply it to as many decks as you like. They have no effect on game play.