How many geared lenses do you have in your kit? If the answer is one or more, definitely get the Gear Drive addition for the Silencer. The Gear Drive lets you use the Silencer as a geared follow focus instead of the included belt drive. Is one drive better than the other? While they're both awesome systems, they're good for different purposes, and the Gear Drive makes focusing geared lenses much easier and more compact.
Silencer Gear ...