2 diffusers 2.4mm for your BBW cup.
The diffusers in the cups are designed to work only with the Furick cup brand cups. We recommend you buy a few spare diffusers to have, they are somewhat consumables and will eventually need to be replaced. The diffusers must be installed like you received them installed and must seal tightly around the cup or you will have poor results. They are designed to have a gap between the 2 layers of screens and it is recommended you install them back that way, It may take a few tries to get the screens in properly but have patience, the cupped side goes in first.