Habitrail OVO Curve allows you to install a curvy, elongated space to your Habitrail setup. 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.