Since this is Japan’s annual “High Class Pack” set, its main attraction will be its enormous amount of alternate art secret rares.
Each Terastal Festival ex booster pack will contain 10 cards instead of the usual five, including a guaranteed Pokemon ex. The larger packs, guaranteed hits, and secret rares are what define a “High Class Pack” set.

Each Terastal Festival ex (SV8a) Booster Box contains 10 booster packs each.