Most common suspension is our letter A. The suspension spring A is the most common suspension spring needed. If working with a floor clock it would be suspension A2 or A3 depending on the pendulum. For a pendulum with a 6 1/2 inch (165mm) or less bob diameter, use suspension A2. If larger, use suspension A3. Suspension A4 is only for huge clocks with tubes hanging off the back of it (tubular bell units) with a very heavy pendulum.
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