This is an adjustable link that has conventional threads on one end and reverse threads on the opposite end. This enables you to make vehicle adjustments without having to remove the link from a vehicle completely.
A turnbuckle is a device for adjusting the tension of ropes, cables, and tie rods. It normally consists of two threaded eyelets, one screwed into each end of a small metal loop, one with a left-hand thread and the other with a right-hand thread. The tension can be adjusted by rotating the loop, which causes both eyelets to be screwed in (or out).