Keep a close eye on your feathered friends dining by placing this ClearView Window Tray Bird Feeder in your window. The semicircular top and base of the unit rest inside your home and a polycarbonate window here keep the birds visible. Two rectangular adjustable PVC panels, form the front of the item and allow the unit to be mounted into most single and double-hung windows from 27" to 36" wide. The main reason we have chosen the clear panel is that a lot of bids are territorial and would attack a mirror reflection of themselves. Our design and having a clear viewing panel help prevent the birds from seeing a reflection and trying to attack their own reflection, which could harm the bird.