Habitrail OVO Cube allows you to add multiple routes to your Habitrail setup so that you can have your hamster burrow back through different trails from one point. It has air vents to improve air flow and ensure that your hamster's home is always fresh Based on extensive behavioral studies, Habitrail OVO housing and accessories are designed to help enhance your pet hamster's quality of life. Completely redesigned, re-tooled and reinvigorated, OVO brings even more interesting and entertaining venues in which hamsters can explore, burrow, snooze, exercise or simply chill out.