Pendulum Drive Mechanism This pendulum drive unit can be used in many wall clock repairs. This pendulum drive mechanism will move pendulums up to 350 g (12.3 oz), up to a length of 990.6 mm (39"). Unit mounts inside the clock case with 4 pre-drilled mounting holes. Measures 139.7 mm (5-1/2") (H) x 63.5 mm (2-1/2") (W) x 50.8 mm (2") (D). The detached battery compartment measures 60.3 mm (2-3/8") (H) x 54.0 mm (2-1/8") (W) x 25.4 mm (1") (D). Runs with 2 C batteries. Made in China. Pendulum and batteries are not supplied with the unit.