This medium sized willow ball is tightly woven, ensuring that this ball will last a long time. The natural peeled willow gives it a nice cream color and makes it ideal for birds and other small animals as well as bunnies. Great for chewing, rolling and/or tossing in the air. The balls range from 3.75 to 4.0 inches (9.525 - 10.16 cm) in diameter and are hollow inside.