Both sizes fit 40-oz tumblers in the interior and exterior cup holders. The biggest difference is laptop capacity and how much you usually carry. Medium Fits devices up to 9” x 13” and 15” diagonally (13–14” laptops) Great for everyday use, lighter carry loads, and a more compact feel Large Fits devices up to 10.5” x 14” and 16.5 diagonally (15–16” laptops) Best if you carry extras like notebooks, chargers, planners, or travel essentials If you want help choosing, let us know what you typically bring with you. We’re happy to recommend the perfect size!