This window barrier measures 31" high and offers extra safety for curious toddlers. It can be used on casement and double-hung windows, and mounts in front of the glass for extra protection. Can be mounted to the surface of the window frame or within it. Quick release hardware allows adults to open in case of emergency. Heavy-duty steel style construction fits openings from 28" to 42 1/2". Add up to two extension kits for openings up to 63". See item 3330w for example of surface mounting of this window guard.