The RGM-89J Jegan Normal Type is an upgraded version of the old RGM-89 Jegan that took over as the basic Jegan model by U.C. 110. It has increased generator output and its sensors as well as drive system have also been slightly tuned up. Although the stick-type control system has become the mainstream in the U.C. 120s, this machine continues to use the arm raker mechanism, and is considered to be the last MS to use this mechanism. Externally, it differs only slightly from the initial mass production type in its backpack, dedicated beam rifle, and shield.
In the early UC 0100s, the Earth Federation Forces (EFF), whose arms budget was reduced as the time period was relatively peaceful, began looking for a reliable but cheaper alternative to the RGM-89 Jegan series as the machines were considered quite expensive to maintain due to their large size. As a result, Anaheim Electronics created the smaller RGM-109 Heavygun. However, as this new machine was basically just a "mini Jegan", the EFF did not fully replace the existing Jegan units, but rather continue to upgrade them while searching for a suitable replacement.