The High Strength Double Socket Plastic Arm has a 1.5" dia. Ball Socket at one end and a 1.0" Socket at the other. This combination arm allows a 1.5" (C size) dia ball accessories to be connected at one end and the other end has a socket for a 1.0" (B size) dia ball accessory. A tightening screw on the side of both arms enables the sockets to clamp firmly to the rubber ball accessories. When loosening the side screw on either arm, the corresponding ball easily removes from the socket if required. Commonly used to adapt B size RAM balls to C size RAM balls.