The Habikat window is easy to install and clean. An instruction manual with pictures is included for easy installation. The Habikat window installs much like a removable air-conditioner and is secured by the weight of the window and a safety "L" shapped bracket for extra protection. The "L" attaches to the top of your window where it locks, thus securing the window which holds the Habikat in it. The three windows panes are made of durable polyethylene. The top and bottom of the unit is solid. The solid windows are air tight, if installed properly, so weather (rain, snow, etc) cannot get in. However, there are 4 air vents in the front of the unit so your cat can get fresh air. Four white plugs come with the window so you can close these air vents when desired. Strong enough for big cats.