The RAM-D-254-WD1U consists of a 2.25" diameter rubber ball, connected to a 2.5" diameter plate containing 7 holes total: the industry standard 4-hole AMPS hole pattern and a 3-hole 120-degree hole pattern. This component can drill down to any flat surface or connect to any RAM holder or cradle. The D Size ball is compatible with any other RAM D Size ball & socket components.