Some players find it comfortable to have an armrest that acts like a pivot-reference when playing in thumb-position. The armrest follows the outline of an acoustic bass body, and more precise; only the front line where you would rest /pivot your arm while playing in thumb position.
The armrest is made from carbon and can easily be attached or removed. The neck attachment hinge rod is hollow, so the thread to attach the armrest can be fed through this tube and then tightened with a thumbwheel on the opposite side.
