Base Kit for FUJIFILM GFX ETERNA 55 includes:

Top Plate (FUJIFILM GFX ETERNA)
Attaches to the top of the camera and provides 1/4-20 and 3/8-16 threaded holes with ARRI accessory pins, and M4x20mm ARRI standard threaded holes.

Segmented design allows the original ETERNA handle to be installed in the camera's dovetail slot over the Top Plate. When the top handle is removed, the smaller section of Top Plate can be added.

Baseline 15mm LW (FUJIFILM GFX ETERNA)
A baseplate that holds 15mm lightweight rods at the correct distance from the center of the lens and attaches to the bottom of the camera by three 3/8-16 screws.

The center of the LW 15mm Bracket has a 1/4-20 vertical support post, which can be used to support lens adapters like Metabones, etc.