The RAM-B-238U ball base consists of a 1" / 2.54cm B size rubber ball connected to a 2.43" / 6.17cm / 6.17cm x 1.31" / 3.33cm / 3.33cm diamond plate. The diamond plate features two holes that measure 1.912" / 4.86cm from center to center, matching the industry-standard AMPS hole pattern. This diamond ball base is compatible with a wide variety of RAM® device holders and cradles.