There are three versions of the retractable thrusters, one model design for direct mould-in (SR), and two designed to be mounted on a flange (SRV and SRL). The flange can be a mold-in base from Side-Power, or the boat builders can manufacture their own base in materials suited for their hulls or as part of their basic hull design.
The flange mounted models have thruster unit in a casing that will be bolted to a base. This allows for easier installation in hulls made from different materials, as well as in series production where you do not need to mix laminating and engineering type jobs.
For all installations where the mould-in base is not an integral part of the hull design, and SRF mould in base should be used for installation.