The GM Trainer is a mobile suit used for training by the Earth Federation Forces. It is a part of the Mobile Suit Variation line.
During the One Year War, the number of pilots had decreased due to the Battle of Loum, and the war had shifted from fleet battles between battleships and fighters to hand-to-hand combat between mobile suits, making the lack of trained mobile suit pilots a serious problem. Additionally, since the deployment of various GM type MS had begun, there was a need to train pilots to be more in tune with the GM, and this machine was developed for combat training to solve these problems.
The GM Trainer has two cockpits, one in the abdomen for the trainee pilot, and another above it for the instructor. A portion of the front, left section of the instructor's cockpit is made of glass, allowing the naked eye to see what is going on outside. The performance of the GM Trainer is almost the same as that of the GM, but due to the exclusion of many armaments for cost reduction and the low quality of the armor, this machine is incapable of withstanding actual combat.