In the year 0086 of the Universal Century, the GM II, the main MS of the Federation Forces, was usurped as the main mass-produced MS by the Hizack, which was developed under the leadership of the Titans and offered superior overall performance.
However, because the Hizack was a mix of GM and Zaku, it was plagued by constant mechanical problems. As a result, the Federation MS Development Department once again began development of a later model based on the GM II, with improved overall performance for a mass-produced machine.

Based on the current GM II, the OS was completely redesigned based on operational data obtained from Captain Kou Uraki's Gundam Mk-II 4, which was deployed in combat at Oakley Base. Accordingly, the generator output was increased. The Mk

HGUC RMS-179B GM II Late Model Prototype | モトッチ's Gunpla works