Mini-Sized Deck Protectors are specifically sized for Yu-Gi-Oh! & other smaller gaming cards. Deck protectors are a tougher and more uniform version of traditional card sleeves, made of polypropylene, and specifically designed to snugly fit collectible card game cards. The first deck protectors were clear, but soon after, deck protectors were offered with opaque black backs, which would obscure the actual back of the card, allowing worn cards to be used without "marking" the deck.