These horns are a small size great for msd. (other sizes listed separately) The diameter at the base is about 12mm wide with a magnet slot for about 6mm diameter disc magnet that is about 3-4mm tall (same size base as the yosd, but this version is longer/taller then the yo).
Buy magnet separately and super glue or epoxy the magnets in place. The horns do have a hollow cavity to help reduce cost and weight.
can be dyed, painted, etc.