Tire Replacement for BIS Trolley or Crate Caster The Best in Show Trolley/Crate casters are designed for a low speed application. The casters feature Foam Filled wheels that have NO air in the tires, thus eliminating the possibility of the wheels emerging flat. Our Foam Filled wheels do not have resilience. They provide traction and a wide footprint which enables them to roll on grass, dirt, sand, mud, snow and gravel. Foam Filled wheels have a higher initial cost than airfield pneumatic wheels. However, overtime, they may prove to cost less because they last longer and avoid down time due to the loss air, The BIS Trolleys/Crates are designed to move easily with Foam Filled Wheels because they require less effort to move than pneumatic wheels theater under inflated. Please note that Foam Filled Wheels may wobble due to the uneven weight distribution of pets or items in the trolley OR due to a light weight load OR due to the floor or ground surface. WOBBLING WHEELS ARE NOT DEFECTIVE. The replacement wheel will fit the stationary and the lockable swivel casters on the Best in Show Trolleys/Crate Wheel Base.