Plastic black or grey quality knobs with different diameters. Nut lock.
Specifications:

1. colour: black
2. Ø: 36mm
3. dimensions:
   1. A: 6mm
   2. B: 36mm
   3. C: 20mm
   4. D: 25mm
   5. E: 4.5mm
   6. F: 11mm
   7. H: 21mm