Early Release Boxes: Full Boxes of Set Boosters are available for purchase and pickup during the week of Prerelease, September 17-23.
Each box of Set Boosters will be accompanied by the Innistrad Midnight Hunt Buy-a-Box promo (while supplies last).
Each Set Booster comes with a guaranteed rare or mythic rare card and more—a foil card, beautiful art card, thematic commons and uncommons, plus a chance at a card from The List—making it exciting to open and add to any Magic player's collection.
Get more details in this article from Wizards.
Each Set Booster Box contains 30 Set Boosters