The Travel Backpack 18X14X8 by Ecohub is a stylish and practical choice for Spirit Airlines passengers and any other airline with strict size rules. With a solid black nylon material, this unisex-adult backpack has a capacity of 30 liters and dimensions of 7.87 x 12.99 x 18.11 inches, making it the perfect size for underseat storage. Weighing only 1.6 pounds, this lightweight backpack is easy to carry while on the go, offering convenience and functionality for travelers.