RAM Ball 2.5" Diameter Base with 1" ball. This base has an AMPS/NEC hole pattern arrangement that allows you to attach to any existing hole pattern

When ordering this part, please make sure you also order the relevant base/arm mount/cradle to give you the complete solution. A selection of different mounts to attach to cradles is shown below and these will fix to the any cradle you may have which has a diamond socket.