High quality white finish aluminum construction installs easily into most aluminum sash window styles. Minimum sash window height requirement is 15.0625" Locking rigid flap is made of unbreakable clear Lexan to allow pet to see through opening and is non-toxic for added safety Recommended for pets 2 to 25 Pounds Need Assistance? E-mail Ideal Pet Products expert US-based customer care specialists seven days a week!