MTG: Core Set 2020 Deck Builder’s Toolkit – Rules of Play says:

Contains:

• 1 pack of 125 cards (included cards are the same in every Deck Builder’s Toolkit)
• 4 fifteen-card booster packs from recent Magic sets
• 100 basic land cards
• 1 deck builder’s guide
• 1 Magic quick reference booklet
• 1 reusable card storage box