【Environmentally Friendly Material】: Hamster exercise wheels are made by high quality environmental friendly plastic materials to protect pet health. This product uses a new PP material with a lock. It is easy, convenient and quick to install this product! 【Hollow wheel】: The design of making both sides of the running wheel hollow allows hamsters to breathe easily and do aerobic sports. There are several reliable air holes in the wheel, your pet can have a long time fun in the wheel! 【Transparent Wheel】: Pets can have fun in the large and transparent hamster running wheel, and you can observe your pet’s every movement, it’s interesting! 【Simple installation】: Thanks to the lock, you only need to press it lightly to assemble this product, it’s easy to install! 【DIY Combination Toys】: This small hamster wheel can be connected to other tubes, allowing you to create other combinations to increase the difficulty of the game for your pet!(15cm)