The RAM-103U-B consists of the 1.5" diameter ball and socket system with one open socket end. This mount is designed to be used with any of the RAM mounting bases or cradles with a 1.5" diameter...
The RAM-B-103U-A consists of a 2.5" round base and SHORT double socket arm that will accept 1" ball bases. The round base contains pre-drilled holes, including the universal AMPS hole pattern...
The RAM-B-103U-C consists of a 2.5" round base and LONG double socket arm that will accept 1" ball bases. The round base contains pre-drilled holes, including the universal AMPS hole pattern...