An upgrade of the original Gundam Sandrock to make it capable of space combat. Verniers were added to the shoulder, back skirt, backpack, and legs to increase mobility in space. As the added backpack vernier took the place of the mounting point for the shield, the Gundam Sandrock Custom can no longer use the Cross Crusher. It also gains a beam machine gun for better mid-range combat capability in space. Like the original, the Sandrock Custom can function as a commander unit for team operations.

As the military and political strife plaguing the Earth Sphere in AC 195 would reach a decisive conclusion in space, Quatre Raberba Winner returned to space with his Sandrock to join the battle. Aboard the independent battleship Peacemillion, Gundam supporter Mike Howard and his team upgraded the mobile suit for space combat, creating the Gundam Sandrock Custom. Later, over Quatre's protests, Gundam pilot Heero Yuy temporarily installed a component of the XXXG-00W0 Wing Gundam Zero's infamous Zero System into the Sandrock Custom, allowing Quatre to coordinate the other Gundam pilots in an assault against White Fang's mobile dolls. The Zero System was removed by Quatre afterwards.