This is Dex (Lindsay's Delightful Dexaroni) and he is a puppy that was stepped on in the whelping box, by his mom. It damaged his rear legs and they were amputated and he has 2 stumps now, His owner (the breeder) put him in a Walkin' Wheels (6in. Strut x 4in. wheels) at 12 weeks of age and is upgrading it as Dex grows (now going to a 9in. strut x 12in. wheel). He said Dex is a typical puppy and does very well in the cart.