Clock Crank Chime Keys Clockmakers Tools Sz 11 5.00mm This is a new set of two size 11 clock keys. They are used to wind clock mainsprings. You receive: One #11 clock key with a 5.00 mm hole One #11 grandfather clock crank key with a 5.00 mm hole Newer versions of the item shown may be shipped, as a result, there may be a slight variation in color and design.