The Federation's successor to the versatile but terribly underperforming GM mobile suit series. Tougher armor and much more power ensured the Jegan was a much greater machine than the countlessly refitted GMs it was replacing.
The RGM-89D Jegan D Type is a minor update of the type, with more flexible loadouts and minute improved sensors and thruster packs. That not much was changed showed a degree of refinement in the original design that enabled it to remain at the cutting edge of mass produced MS even at the rapidly evolving environment of the Universal Century. The Jegan was later developed into the Jesta and the ReZEL mobile suit designs.