2pc Brass Clock Winding Key set for clocks with square winding shafts. The odd sizes are: 3mm-1/8 inch (3), 3.5mm-9/64 inch (5), 4mm-5/32 inch (7), 4.5mm-0.174 inch (9), and 5mm-13/64 (11). Measurements are approximate. The Even Sizes are: 2.75mm-7/64 inch (2), 3.25mm-1/8 inch (4), 3.75mm-0.14 inch (6), 4.25mm-11/64 inch (8), and 4.75mm-3/16 inch (10). Measurements are approximate.