Well-armed for its size, its four turbolasers and dual-proton torpedo launchers made it a formidable adversary for a lone starfighter. Furthermore, its frontal armament of general purpose warhead launchers (usually fitted with proton torpedoes), laser cannons and ion cannons made capable of assaulting or capturing capital ships and space stations. Although not as swift as a starfighter, its top speed was comparable with all but the highest performance cargo and troop transports. Despite being more than twice as large, with all these features—especially the evasive capabilities—ETR-3s were reminiscent of the Clone Wars-era LAAT/i.
The ETR-3 was a further development of the Gamma-class ATR-6 assault transport. The ETR-3 retained the ATR-6's main hull, giving it approximately the same size and troop-carrying capacity. However, the ETR-3 carried an additional dorsal pod, reintroduced forward-firing laser cannons, and had stronger shields and armor. That being said, the ETR-3's improvements were not a significant advantage over the ATR-6, which remained the mainstay in the forces of the Imperial Navy. It was also designed in mind to escort construction vessels when establishing planetary outposts on un-pacified worlds. With the capacity for carrying up to 40 troops, it was able to transport an entire squad of speeder bikes. The ETR-3's sturdy design, being suitable for both military and civilian activities, made it popular throughout the Galaxy. Capable of significant modification, the craft took on a variety of roles from simple transport to a platform for testing Admiral Zaarin's TIE Experimental Project of advanced and new technology.