MaterialPlastic ColorBlue 12cm Target SpeciesHamster Environmentally Friendly Materials: Hamster exercise balls select high-quality environmentally friendly plastic materials to protect the health of pets well. It is produced with brand-new PC material, with lock design, easy installation, convenientand fast! Hollow Runner: Hollow design on both sides of the running wheel makes the running wheel more breathable and allows hamsters to aerobic exercise. There are multiple vent holes on the ball, which is safe and breathable, and your small pets can play init for a long time! Transparent Ball: Pets can play in the transparent and large hamster ball, and the owner can observe the pet's every move. So cute! Easy to Install: Adopt the lock design, it can be molded with a light press, easy to install! DIY Combination Toys: This small hamster ball can be connected to external pipes, and unlimited extension, allowing you to DIY combinations to increase the difficulty of pets!