The RAM-B-189BU consists of a double 3.3" twist lock suction cup base. Included is a hole pattern that will allow attachment to all RAM bases that contain the universal AMPs hole pattern.
RAM® Universal Double Ball Mount with Two Round Plates
RAM® Double Ball Drill-Down Mount with Diamond Plate
RAM® Double Socket Arm with Round Plate
RAM® Twist-Lock™ Suction Cup Base
RAM® Dual Adapter Plate for RAM® Twist-Lock™ Suction Cups