Habitrail® OVO Tee allows you to add an upward or sideway trail or add a water bottle to your Habitrail® setup. The Tee has air vents to improve airflow and ensure that your hamster's home is always fresh The complete line of Habitrail® OVO housing and accessories is based on extensive behavioral studies of pet hamsters and is designed to help enhance their 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.