Cast polyurethane with cast iron hubs provides low rolling resistance and smooth and quiet running. It is gentle on the surface and does not stain. Banana is highly durable and resistant to oils, greases and many chemicals. It is elastic and returns to its round shape after resting load, and has high resistance to metal shavings, gravel, etc. The cast iron hub makes the wheel a robust wheel, with great resistance to shock loads and horizontal stresses.