This is a black nylon large wing nut with a zinc plated steel insert. These German shaped wing nuts have more rounded "wings" than the others. These are the BPF 50 and BPF55 models.
BPF 50 and BPF 55 nuts are Type O wing nuts, i.e. through nuts.
These plastic wing nuts have the quality of having large fins.
The large wings of this wing nut allow a good grip and can therefore be used without tools. This ease of use is therefore simple for any type of assembly.