Clock Pendulum Bob only for a wood stick pendulum. The bob will take either the 3/4 inch wide stick or the 1 inch stick both. A pendulum bob is the round disk at the bottom of the pendulum and the diameter is the measurement from one side to the other. To select the proper bob size you would need to know the inside width of the clock case. You should have at least 2 inches on each side of the pendulum bob so it can swing in the case without hitting the sides. We have some wood sticks available also and there in the drop down list with the bobs.