A 5/8 rose joint threaded left-hand. A rose joint carries a spherical bearing in its head, so the arm can articulate through suspension travel without binding while holding its geometry accurately, which is why they replace rubber bushes on competition cars. The left-hand thread is the point of this variant: fit a left-hand joint at one end of an arm and a right-hand joint at the other, and the whole arm becomes a turnbuckle you can lengthen or shorten in situ without unbolting anything. That makes corner-weighting, toe and camber adjustment quick. Always fit lock nuts and check thread engagement remains adequate at full adjustment.