Each March of The Machine: The Aftermath - Collector Booster Box contains:
• 12 March of The Machine: The Aftermath - Collector Booster Packs
• 6 Magic: The Gathering Cards + 1 Foil Token Per Collector Booster Pack
• 4 cards of rarity Rare or higher in every pack
• 5-6 Foil Cards per pack
Starting with The Brothers' War, Buy-a-Box Promos will only be available for in-store pick-ups and purchase while supplies last as stated in Wizards of the Coast's article here.