"The RAP-201U-B, short double socket arm, has a socket at both ends that accommodates 1.5" ball bases. A single spring inside the arm opens the end sockets, allowing you to pivot the ball and socket connection. This socket technology allows for almost infinite adjustment and perfect viewing angles. Dimensions: Overall Length: 3.5" Socket-To-Socket Length: 2.25" Material: High Strength Composite Ball Size: 1.5" Rubber Ball Size"