hamster balls are hollow spheres made of clear plastic into which hamsters, gerbils, degus and other small rodent pets are placed, allowing them to run around outside their cages without the risk of running away or getting lost under furniture. hamster balls have been manufactured and sold since at least the 1970s. [3] most are made of durable transparent plastic with air holes and a small door or lid to allow the owner to insert or remove the hamster from …