An isolinear rod was a type of information storage technology used by the Cardassian Union. Holosuite programs could be stored on isolinear rods. (DS9 novel: Sacraments of Fire) Quark used isolinear rods to gain access to the various Cardassian systems on Deep Space 9. Different colored rods, which included crimson, jade, topaz and sapphire, had different chances of being detected. (DS9 episode: "Babel", DS9 novel: The 34th Rule, DS9 - Mission Gamma novel: Twilight, DS9 novel: Warpath)