Cluster Backlog Items (CBI) are the individual elements (Backlog Items) of a Cluster Backlog and describe work for a Cluster. The size of a CBI is initially not limited. It must be small enough in size or devided (refined in the Cluster Backlog Refinement) into several individual items that can be done in one ClusterCycle, before it can be pulled into the Cluster Cycle Backlog during the Cluster Planning.
Cluster Backlog Items can be of different types, e.g. a Feature of an Application or System, or a Module Version. It can also be the description of a Knowledge Gap or an Issue, or the integration and creation of a new System Version (System Increment).