This is a custom-made 4-wheel walker for small dogs. It's made of aluminum, so it's surprisingly lightweight and moves smoothly. The length and height are adjustable; the photo shows a dachshund using it. *The height can also be fine-tuned with the belt, allowing for the perfect position for each individual dog. It's for dogs that are bedridden or have paralysis. The purpose isn't necessarily to walk with a wheelchair, but rather for rehabilitation. Since it's a 4-wheel walker, it also allows for a change of scenery during walks.