Environmentally friendly material: Hamster running wheels are made of high quality environmentally friendly plastic materials to protect pets' health. This product uses a new onePC material with lock. It's easy, convenient and quick to install this product! Hollow wheel: The design that both sides of the wheel are hollow allows hamsters to breathe easily and do aerobic sports. There are multiple reliable air holes in the wheel, your pet can have funlong in the wheel! Transparent wheel: Pets can have fun in the large and transparent hamster racing wheel, and you can watch your pet's every move, it's interesting! Easy Installation: With the lock, you just need to press it lightly to assemble this product, it's easy to install! DIY Combination Toy: This small hamster wheel can be connected to the other tubes, allowing you to create other combinations to increase the game difficulty for your pet! It can be combined with rails and tubes. A variety of combinations allows hamsters to expand their range of activities. Installation Instructions First insert 4 sticks at a time. Second, align it with the notch and insert the clear cover. Third, rotate the cover into place. Finally, repeat the above steps, done. Warm Prompts: 1. Do not use this racer ball on sloping floors, tables or near stairs, falling or running the balls too fast may damage your pet. 2. According to some customers and friends, the racing ball cover always falls off after being twisted. As explained here, there is a concave on the cover clip and a convex on the corresponding attachment point of therolling ball. Only when both points are anastomoses can the cover be attached correctly No more than 30 minutes at a time. Do not leave the animal alone in places that are unattended or hot in the sun. Wash with clean water after each use.