I am still 98% sure that isn't mu's body :S Mu's main body was super saiyan utilized during the fight with both insect queen then king, and then not involved afterwards. The body that became "mu sub" was the earth tier copper mouth, and said form got wasted in space after the whole onslaught with the dimensional assassin. The body then reverted to female, and we went through the silver planet thing up to now. When femu had arms destroyed and they introduced "ring mu"(rinmu), I assume that was crafted out of the heart of the general, and that femu was restored with what was left.The new design for femu's hips looks very unnatural, but the duo fighting concept is nice to see. So, if we need a refresher....
Real mu -> dunked into holy blood and turned supersaiyan-dragon-soultier.
Dragon queen mu -> insect queen's body with mu's consciousness.
dumbmu-> also known as one of the cutest things ever, is the dumbest incarnation, made of beiyang's main cannons.
Musub/femu->copper mouth's body with mu's consciousness which was the one that got returned to female state after assassin fight.
ringmu->made of the general heart, we aren't sure how much of it was used for his creation, the rest I assume was used on femu's repair/improvement.
Possible material sources include the body duhmu ate, and the material eaten from the assassin, and a couple others I don't remember all the details of. There was also the holy blood lake which had weapons at the bottom, but pretty sure that went to ding yuan.