Habitrail® OVO Windows allow you to block off pathways, while maintaining maximum air circulation, thanks to air vents located all along the perimeter of each window. This replacement pack includes 3 colourful (red, blue and lime) OVO Windows. 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.