RAM MOUNTS 1.5-Inch Ball Mount with Spline Post Adapter, Black 1.5" Rubber Ball Size High Strength Composite Offering the patented RAM rubber ball, socket and ratcheting feature, you can rotate the arm 360 degrees The RAP-114-AP-RBU consists of a quick release spline post base and RAM-ROD Revolution ratchet arm with single open socket for 1.5" ball bases Lifetime warranty