ZxRage, of course, is correct.
Regarding the need for these two rear tie braces, I doubt they do anything for the car. Look at the first pic. See the gigantic aluminum suspension piece going over the top of the differential? Right, the piece the aftermarket bar is connected to. I doubt a dinky little bar like that will make much difference. I have spent plenty of time under the differential and I can tell you that the rear suspension connecting the two side is built like a brick **** house.
When GTSpec was developing these parts, they posted on my350z. At the time, I questioned the need for these parts. I still do.