More differences:

- Serpent has the largest diameter.
- Picco and R&B are the same and a bit smaller than the Serpent
- The Novarossi is as big as the Picco but blue
- I have seen a prototype R&B based on the Novarossi but it was orange
- The Mugen is the smallest but you can only use Mugen filters and that filter is not as good as you want it to be.