Apeks screw set for mounting wing gears (accopling wing to backplate).
Made of stainless steel, they have a 20mm long screw. The inner faces of the threads have a rubber gasket that prevents them from unscrewing by themselves.
Widths can be set from 25mm to 16mm. The minimum width they reach is 11mm but from 16 onwards, the stud protrudes from the rear.