Foam Wheels & Struts Sets For Small, Medium and Large Rear Walkin’ Wheels Wheelchair Frame. The metal struts snap into the leg of the wheelchair frame and adjust to the height needed for your pet. Struts are adjustable within a range of 3 inches and come in 6 different sizes: 6", 9", 11″, 12", 15" & 18″. The foam wheels are perfect for all breeds and great for all terrains. They feature a dense foam interior with an outer rubber layer. These wheels will not puncture, they wear extremely well, and are easy to clean. Sizes available: 4″, 8″,12″ & 16″.