The 2026 Topps Series 1 Baseball Celebration Mega Box arrives just in time for MLB Opening Day, building on the flagship release and continuing the celebration of 75 Years of Topps Baseball Celebration delivers the 350-card Series 1 base set, featuring today’s biggest stars, top rookies, Future Stars, League Leaders, and team cards. Collectors can look for 75th anniversary-themed inserts and parallels that honor the brand’s rich history and legacy.