I have one like this.
Wow.
I was asking about making robots after finding a bag with SG90 9g servo motors just like yours. Mine look very fragile, all plastic, including the gears. Not very precise either, the gearbox has a lot of backlash. Even if I disregard the backlash, they still have bad repeatability. For the same control signal, when going back and forth, the resting angle is almost never the same.
At least they were cheap, $1.1/pcs from Aliexpress.
Does your motors have enough force to lift the robot legs, or is it walking by dragging the legs?