It is designed for dog breeds that weights 30 lbs and less. The K9 AIR Plus - Small will fit dogs with the length of 14-17 inches and have a girth up to 27 inches. Typical dog breeds that will fit this size backpack include Chihuahua, Maltese, Teacup Yorkie, Pomeranian and Papillion. Use it as a dog travel bag for hiking, bikes, subways, shopping, motorcycles, skiing, dancing..heck the possibilities are endless! Does your dog suffer from anxiety, depression, or have a physical disability? Or maybe just older or doesn’t have the stamina for your next big adventure. Problem solved!