CT-5587, nicknamed Rex Bactapack, was a special clone born on Kamino. Rex served as a special infantry vanguard, who was always the first into battle to help his brothers. He is an expert shot with a blaster. He joined the famed 501st Legion shortly after his graduation day from the Kamino Training Facility. He lead an elite group of clones, Special Forces unit 994, code named, Bacta squad, an infantry unit that leads the army into battle, along with Captain Rex's squad.