Environmentally friendly material: Hamster running wheels are made of high quality environmentally friendly plastic materials to protect pets' health. This product uses a new one_x000D_PC material with lock. It's easy, convenient and quick to install this product! _x000D_ 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 fun_x000D_long in the wheel! _x000D_ 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! _x000D_ Easy Installation: With the lock, you just need to press it lightly to assemble this product, it's easy to install! _x000D_ 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! _x000D_ _x000D_ It can be combined with rails and tubes. A variety of combinations allows hamsters to expand their range of activities. _x000D_ _x000D_ Installation instructions _x000D_ First insert 4 sticks at a time. _x000D_ _x000D_ Second, align it with the notch and insert the clear cover. _x000D_ _x000D_ Third, rotate the cover into place. _x000D_ _x000D_ Finally, repeat the above steps, done. _x000D_ _x000D_ Warm Prompts: _x000D_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. _x000D_ _x000D_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 the_x000D_rolling ball. Only when both points are anastomoses can the cover be attached correctly _x000D_ _x000D_ No more than 30 minutes at a time. _x000D_ Do not leave the animal alone in places that are unattended or hot in the sun. _x000D_ Wash with clean water after each use.