Oak leaf style cuckoo clock pendulum comes in four lengths. If you do not know what length to get it is the 8 inch most likely. The longer ones are pretty rare and are for a very large cuckoo clock. This one has a leaf that is 4 1/2 inches (11cm) long and 2 1/2 inches (6cm) wide. The leaf slides on its stick to time the clock, if the clock is running fast in time the leaf slides down. If slow then slide the leaf upward more.
8 Inch (20mm), 15 Inch (38mm), 17 Inch (43mm)