A '''Duel Disk''' (デュエルディスク ''Dyueru Disuku'') is a piece of [[Duel]]ing equipment attached to the left forearm within the ''[[Yu-Gi-Oh!]]'' franchise. They were first manufactured by [[KaibaCorp]] as a portable form of [[Dueling Arena]] s used in the early part of the [[Yu-Gi-Oh! (anime)|Yu-Gi-Oh! second series anime]]. They use a portable hologram generator to display [[Duel Monsters]] cards and in the case of the Mark 1, the player's [[hand]]. Cards that are played are placed on the Duel Disk's [[blade]]. Since their introduction in the [[anime]] and [[manga]], they have become a fundamental necessity among [[Duelist]]s.