The locking 3.25" Rubber Suction Cup Base has a standard RAM double hole diamond shaped end. The suction cup is designed to have an extra strong hold on any smooth non-porous surface, but for best result, mount the suction cup on a glass surface. The diamond shaped end has two holes 1.912" from center to center. This will connect to RAM-B-238 Diamond Plates Series, the universal industry standard AMPS hole pattern or directly to the back of the RAM Composite Holders. This suction base does NOT have, or include, a RAM 1" rubber connection ball. Two self tapping screws are supplied with the suction cup base.