A fast courier in the Vorkosigan Saga was a military ship with very little space for cargo, crew, or weaponry. The job of a fast courier was to go very quickly, period. Fast couriers often operated as picket ships within fleets or convoys. They seemed to vary in size somewhat: The one that conveyed Miles Vorkosigan, Ekaterin Vorkosigan, and Roic to Quaddiespace had so little space for people that Roic had to bunk with the pilot. One in Shards of Honor had enough room to convey an extra passenger and seventeen uterine replicators.