Why there is a rubber cap on the top of NOMAD? What is it for?

The rubber stopper/rubber cap is designed to cover the small screw inside the hole. If you remove the stopper, you’ll find a tiny screw beneath it. This screw is used by factory technicians to adjust the distance between the gear and the bearing during assembly. Since the factory ensures proper adjustment before shipping, this screw is typically not needed by end users.

The rubber stopper serves to cover the screw and prevent dust from entering the mechanism.