This is an adapter for boats with Isomat masts (integral track at the front).
This adapter is installed between the platform and the platform mounting feet, and allows the mounting feet to spread out wider.
If you have an Isomat mast and want to mount a radome, satdome, or thermal camera on it, you must use this adapter.
Furthermore, the SM-AD-ISO Adapter can only be used with the SM-14-A, SM-18-R, or SM-18-U mast mount platforms.
So if your radome cannot be used with one of these 3 smaller platforms, you cannot install a mast mount.