The Drop arm will attach to either the Onefinity base or an arm, and is designed to work with "The Tube" on one end, and an Attachment on the other and provide a lower gripping point. 

Not depicted, but it arrives as 2 separate pieces as seen here. The top piece is a mounting point for the arm or Onefinity Base. 

The longer screws depicted here connect the top part to the bottom part, and the 3 shorter screws are what makes that attachment for the arm or onefinity base.