The RAM-103-B-238U consists of the 1.5" C size diameter ball and socket system with one open socket end; RAM-201U-B socket arm is short length at 3.56" end to end with 2.5" socket-to-socket length. This mount is designed to be used with any of the C size RAM Mount bases or cradles with a 1.5" diameter rubber ball. The RAM-238U RAM Diamond Ball Base features industry standard AMPS 2-hole pattern and can be used as an adapter to attach a holder, or a mounting drill-down base.