Universal brass clock key with 5 prongs for winding clocks. The universial clock key covers most of the clock key sizes. Odd sizes included: 3mm - 1/8 in (3), 3.5mm - 9/64 in (5), 4mm - 5/32 in (7), 4.5mm - 0.174 in (9), and 5mm - 13/64 in (11). Measurements are approximate.