A Danube-class runabout that was shrunk to a few centimeters long while investigating a spatial anomaly in 2374.
The USS Rubicon was a Danube-class runabout assigned to Deep Space 9 during the Dominion War era, operating alongside the Defiant on scientific and support missions.
In One Little Ship, Jadzia Dax, Miles O'Brien and Julian Bashir took the Rubicon into a subspace compression phenomenon, and the runabout and its crew were reduced to a few centimeters in size. While they were inside, Jem'Hadar soldiers boarded and captured the Defiant. The miniature Rubicon flew into the ship's internal systems, and its crew helped Sisko and the others retake the Defiant.