The RAP-B-238, composite diamond base, contains a 1" diameter rubber ball connected at right angles to a 1.25" x 2.5" inch diamond plate. The base has two holes 1.912" from center to center, positioned at both ends of the base.
High Strength Composite
1" Rubber Ball "B" Size
If you wish to use a Touratech holder most of them have clamps on the underside, remove them, but keep the screws and nuts and use them to attach a RAM diamond base, RAM-B-238 along the two holes in the centreline.
The RAM-B-238 fits directly onto the back of the TomTom Rider 1 if you wish to use a RAM mount.