You would choose one of the following and report it at the truck (if there is no equipment) or equipment level: 

EC – Shipment consists of empty IIT’s covered by Carrier’s bond
EI – Shipment consists of empty IIT’s covered by Importer’s bond
MC – Shipment consists of merchandise and IIT’s. IIT’s covered by Carrier’s bond
MI – Shipment consists of merchandise and IIT’s. IIT’s covered by Importer’s bond