3 Single End Clock Keys This is a new set of 3 size 8 single end clock keys. These are used for winding clock mainsprings. Each has a 4.25 mm hole. You receive: One size 8 grandfather clock crank key One size 8 brass chime clock key One size 8 nickel plated clock key Newer versions of the item shown may be shipped, as a result, there may be a slight variation in color and design.