15Cm diametered space provides enough large capacity. for your lovely hamster & running around, no need to worry that this ball toy will squeeze your pet. Exercise in running about, which makes it more enjoyable for the more motivated hamster to keep in good shape . fun exercise toy to maintain alertness agility, also helps with release their negative emotions. Designed with multiple airflow bands, this exercise ball has great permeability. to the air, not suffocate to; your hamster. Big for hamster yet small for you, its portable size is convenient for you to carry around. outdoors, allows you to use whenever you want to give away. exercise your little pet. Made of high quality plastic material, this ball is durable sturdy, even if the exercise ball collides, it will not break, not easy to break. wear and tear; corrosion.