MEASURE FROM INSIDE YOUR WINDOW TRACK! FEATURES Flexible vinyl flap with magnetic seal at base Slide in plastic locking cover for pet opening Both ends have spring loaded adjustment Pet Opening is centered in unit Safety tempered glass on either side These inserts have an approximate 5 inch adjustment range, allowing for the possibility of moving the unit from one window to another, as long as your window widths fall within the same given range. These units are designed to be inserted into the track that your window glides up and down in. Make sure your channel or track is a t least 1" wide to accept this unit. Make sure you can open your window at least 27 inches high.