The K9 SPORT SACK TRAINER MEDIUM is designed for dog breeds that weights 30 lbs and less. The K9 Trainer - Medium will fit dogs with the length of 17-20 inches and have a girth up to 28 inches. Typical dog breeds that will fit this size backpack include Jack Russell Terrier,Lhasa Apso, Pug, Havanese and Schipperke. Use it as a dog travel bag for hiking, bikes, subways, shopping, motorcycles, skiing, dancing..heck the possibilities are endless! | TRAINER BACKPACK: Do you hate seeing big, sad puppy dogs eyes as you walk out the door for an adventure, leaving your best friend behind? Our trainer dog sports backpack are ideal for owners who want to take their pups with them, but are looking for an economical solution. Our backpack carrier are great for dogs who suffer from anxiety, depression, or have a physical disability. Our pet backpack are also great for older dogs or puppys that may not have the stamina for your next big adventure. | ROUND TALL FAT SMALL: We get it! Dogs come in all shapes and sizes, and not every pet travel bag fits the same. We have your dog covered! Our dog travel carrier is available in multiple sizes from X-Small to XX-Large. We have a dog carrier bag that will fit almost any dog breed. View the product images to the left to find the right size for your dog! Please contact us and visit our website for more accurate sizing recommendations. | SPORT SACK IS THE NEW BLACK: (Tip) For all the chubby dogs out there with a few fat rolls over the collar, our Jet Black dog hiking backpack is very slimming! Jokes aside, Jet Black is just 1 of the 4 stylish colors we offer in the Sport Sack TRAINER, and don’t worry all the colors have a slimming effect! Our dog carrying backpack is designed to keep your dog safe and secure. Its the ultimate dog backpack for hiking! | USA-BASED COMPANY, PERFORMANCE GUARANTEED: Wrong size? No problem. Any issues? We’re here for you. Whatever the problem may be don’t worry we’ll cover it, but we’re happy to hear any good stories and see your adventures with your dog. This puppy backpack is backed by a 60-Day Quality Guarantee. Must be sold by seller "K9 Sport Sack" or warranty is voided.