Its a floor brace bar, they are mainly used for stiffening a car side to side. Not much use for one in a Uni-body car like the J-bodies, J's don't flex much at all in that area. I had one in my 03 cavy coupe, it didn't make much difference if any at all. And I wouldn't use it for a harness bar if that's what you are thinking, it puts the harness straps at way too low of an angle, making the straps more likely to cut your arms off or at least mess up your shoulders when wrecking.
