These units traveled from star system to star system, using chronometric radiation to rapidly age stars to the point that they would expand or go nova, and then harvest the released stellar matter to refuel themselves and create more units through a process Commander Spock described to be similar to a Starfleet transporter, converting energy into matter. Each unit resembled a crimson red "horseshoe crab" as described by Helmsman Hikaru Sulu. The units in general had an average length of twenty-five meters though some units were larger and some units were smaller.