The storm window that I thought was gonna be to big to fit in the frame , turned out to be too small. It was a true pain because I had already removed all the glazing and points, and the caulk had already been squirted out so as to cushion the glass and hold it in place more. So we had to meticulously remove all the caulk from the frame and package back up the useless piece of glass I bought. Now I know for sure the dimensions are 24"X15".