Zwei is one bag, with many possibilities. The German bag designer created a unique system allowing the user to swap from a shoulder/messenger bag style to a shopping-bag tore handle, and then back to a shoulder strap thanks to a magnetic buckle, which also can be disconnected and re-used as a waist strap where necessary (running, etc). You can also add what they call a Klick Fix system to secure any of the three bag designs to the front of a bicycle. Refreshing design and interesting innovation– I hope to get you all an in depth review of some of these bags soon!