The Habitrail OVO Club Trainer is a fun add-on which allows your hamster to exercise. This add-on has two functions: it can be used as an outside hamster wheel and it can be used to create a mobile set-up. When using the trainer as an outside wheel, you can watch your hamster enjoy his daily exercise while he spins around. The advantage of adding the trainer to any set-up is that it attaches on the outside of the habitat so you can actually see your hamster run. The other great thing about the Habitrail OVO Club Trainer is, you can design a set-up which uses the Trainer as movable wheels, allowing you to move your pet's entire home around the house. The Habitrail OVO Club Trainer is a great addition to your hamster's home.