Historical Rules · 19 November 2021
Rule 108.2a
Official source text from the 19 November 2021 Rules release
Most Magic games use only traditional Magic cards, which measure approximately 2.5 inches (6.3 cm) by 3.5 inches (8.8 cm). Traditional Magic cards are included in players’ decks. Certain formats also use nontraditional Magic cards. Nontraditional Magic cards are not included in players’ decks. They may be used in supplementary decks. Additionally, they may be oversized, have different card backs, or both.