Following the triumphant introduction of their R2 model, Industrial Automaton moved swiftly to take full advantage of their newfound dominance in the astromech droid sector. The R4 astromech droid, also known as the R4-series agromech droid, represented a very successful effort to tap into a fresh demographic—the Outer Rim city dweller, more inclined to own a customized landspeeder than an X-wing. Consequently, the R4 agromech droid was engineered to thrive outside the sterile environment of a hangar. It boasted simplicity, resilience, and affordability when compared to earlier R3-series iterations.
The R4 shared a similar external design to the R2 or R3 droid below its dome. However, in order to reduce production expenses, components like the video display and a small fire suppression system were removed. The holographic projector/recorder was kept, but its location was changed to the dome's top. This allowed for the integration of a more economical, less miniaturized unit with a smaller range of rotation. The droid's Intellex VI computer was advanced, but it was optimized for common repulsorcraft designs and specifications for commercially available space transports. The computer's internal layout was less compact to reduce manufacturing costs, resulting in a larger head dome. This design choice also led to the removal of many of the status indicators and features present on other R-series head domes. The R4 was not well-suited for use as a starfighter astromech because its astrogation buffer could only store the coordinates for a single hyperspace jump, making it a one-way trip for pilots.
These droids were robust, capable of withstanding the typical wear and tear of a garage setting as well as, or even better than, other R-series droids. IA was pleased to find that, with routine maintenance, the R4 exceeded its expected lifespan in terms of operational duration, resistance to weather, stability of its personality matrix, and the time between recharges.
Due to their enhanced resilience, R4 units became the preferred "mech" droids among the Jedi. However, because of their interstellar assignments, the R4 droids acquired for the Jedi were often modified to incorporate the more sophisticated R2-style head. This gave them a blend of the R2 and R4 series' most desirable traits. Many of these droids underwent further modifications by technicians at the Jedi Temple to establish a permanent connection with the Delta-7 Aethersprite-class light interceptor, until the Jedi transitioned to the Delta-7B and Eta-2 Actis-class interceptor. Even after this transition, pilots continued to use R4 units in the Eta-2 interceptor.
The R4 gained popularity among mass-market consumers, as well as the freedom fighters of the Alliance to Restore the Republic. They believed that purchasing astromech droids in bulk would raise less suspicion than acquiring starfighter-ready copilots like the R2. The model's affordability and knowledge of general-purpose vehicles were also highly valued by the resource-constrained Rebels. Soon, the droids' conical heads became a common sight in Alliance bases and Mon Calamari hangar bays. Some R4s, equipped with specialized magnetic fault sensors, were employed by the Galactic Empire to identify weaknesses and flaws in the atmospheric containment fields of hangar bays aboard both Death Stars and Star Destroyers.