Manfrotto 123 Clamp Pivoting for Booms for 35mm diameter boom shafts 28mm Stud, 16mm socket

Due to its spring loaded clamping, this cold shoe clamp enables one to one-handedly mount shoe fitted equipment very easily. Its finger screw serves both as a push knob for opening the clamp and for tightening down the clamping securely.
It fits the standard shoe sizes of 18, 20 and 22mm.
The Cold Shoe Clamp is tapped with 1/4″-20 and 3/8″-16 holes on the back side

Ercole MK-9 Mini Ball Head 25mm.

Manfrotto 155BKL Head Tilt-TopDouble Ball Joint 16mm Socket on Both Ends 1x 3/8” 1x 1/4”.