YGO Speed Duel: Trials of the Kingdom Booster Box - Rules of Play says:
Introducing the Speed Duel: Trials of the Kingdom booster set! Upgrade your Speed Duel Decks with 45 new-to-Speed Duel cards and 5 brand-new Skill Cards! The Duelist Kingdom tournament brought together the best Duelists to compete for fame and glory. Some of Yugi's strongest rivals made their first appearance, and this booster set is dedicated to all the challengers that you must overcome to become the champion! Contains 36 booster packs.