YGO 2018 Mega Tins - Rules of Play says:
Each Tin includes three 16-card Mega-Packs containing cards from Yu-Gi-Oh! TRADING CARD GAME Maximum Crisis, Yu-Gi-Oh! TRADING CARD GAME Code of the Duelist, Yu-Gi-Oh! TRADING CARD GAME Circuit Break, and Yu-Gi-Oh! TRADING CARD GAME Extreme Force. These Mega-Packs use the traditional “1 card of each foil rarity” plus a Rare and 12 Commons configuration native to the Mega-Tins, and all cards appearing in the Mega-Packs will be included in their original booster set rarity. Each Yu-Gi-Oh! TRADING CARD GAME 2018 Mega-Tin will also include additional non-randomized variant cards, as well as one unique new card designed specifically for that Tin! These new cards are based on the Decks used by Jaden and Yusei, the heroes of the Yu-Gi-Oh! GX and Yu-Gi-Oh! 5D’s manga and animated series respectively, and are depicted on the Tins with the characters.