Cobra Double Joint Stabilizer. 

Combination disconnect/jacknife knuckle. Use as a disconnect by turning the stabilizer 1 1/2 turns, then slide brass connector and stabilizer from the base. To use as a jacknife knuckle turn the stabilizer 1 1/2 turns then swivel the stabilizer 90 and re-tighten to secure. Connector housing comes with brass connector and bolt.