These keys come with total 10 prongs (Each Key with 5 prong), so this is best item as master key for all your clock. If you owe many winding clock in your stock but always problem for the key. These two keys are solution for you. Most of all winding clock keys available in these 10 prongs. The numbers of key are starting from 4 to 13.  Some extra larges key holes are not available in these keys. ODD Sizes: 3.5mm (5), 4mm (7), 4.5mm (9), 5mm (11) and 5.5mm (13) - EVEN Sizes: 3.25mm (4),3.75mm (6), 4.25mm (8), 4.75mm (10) and 5.25mm (12). Both of these keys are Made of BRASS