2 Single End Clock Keys This is a new set of 2 size 9 single end clock keys. These are used for winding clock mainsprings. One is brass and one is nickel plated. You receive: One clock crank key with a 4.50 mm hole One brass chime clock key with a 4.50 mm hole Newer versions of the item shown may be shipped, as a result, there may be a slight variation in color and design.