RAM Mount Composite Double Socket Swivel ArmComposite Double Socket Swivel Arm The RAP B 200 12U, double socket swivel arm, consists of double 1" diameter open ball sockets with a 360 rotation point at the center of the arm. The rubber ball and socket at each end, and a central pivot point provides unsurpassed adjustability. The RAM ball sockets maximize ball coverage for optimal fit. Dimensions: Overall Length: 3. 69" Socket To Socket Length: 3. 5" RAP B 200 12U comes with rubber balls,