Each assembly adds 2 more shells to your TWinS SSL system. Includes one 2 shell holder. For a 4 shell Molle Mount (Pictured) select that in the Drop down box. A SSL molle unit can be configured for at least 32 rounds, the Pinwheelup to 6 rounds and the Backbone up to 12 rounds. This 2 shell assembly can also be added to your own molle panel gear belt, or attached to the forearm of your shotgun.