15-15.4 Inch: Internal dimension: 15.3" x 10". Compatible with 15 Inch Macbook Pro 2018 2017 2016 / Macbook Pro Retina and Most 13 Inch Chromebook Ultrabook Netbook Laptop
13-13.5 Inch: Internal dimension: 13.8" x 9.3". Compatible with 13-13.5 Inch laptop: 13 Inch Macbook Pro 13 / MacBook Air / Macbook Pro Retina, 13.5 Inch Surface Laptop / Surface Book and Most 11-12 Inch Ultrabook Netbook Laptop Macbook
12-12.9 Inch: Internal dimensions: 12.9" x 9". Compatible with 11 - 12.9 Inch tablet/chromebook/laptop, Surface Pro 6 4 3, Surface Pro 2017, Apple iPad Pro 12.9-inch tablet (also fit with Smart Keyboard) and 11 inch MacBook Air and 12 inch MacBook