Antique double end clock key: there is a key hole on each end of the overall key. The entire key measures 3" inches long. The larger of the two key holes has a circular end and a square interior hole. The exterior circular end measures 7.5mm and the square interior hole measures 4mm wide. The smaller of the two keys also has a circular end and a square interior hole. This smaller end measures 4mm wide, the square interior hole measures 1.5mm. PLEASE NOTE - I have many other keys listed and I can always combine items to keep postage costs low. pic