4 Clock Chime Keys This is a new set of 4 brass clock keys. These are used to wind clock mainsprings. You receive: One size 00 clock key with a 2.00 mm hole One size 0 clock key with a 2.25 mm hole One size 1 clock key with a 2.50 mm hole One size 2 clock key with a 2.75 mm hole Newer versions of the item shown may be shipped, as a result, there may be a slight variation in color and design.