Attaching a Sway Control System from a BulletProof Hitch? to a trailer requires the proper mounting points. The BulletProof 1-1/4" Hitch-Mounted Sway Control Ball is designed to work with the Medium or Heavy/Extreme BulletProof Sway Control Dual Ball Mounts. The ball is secured with a lock washer and nut to prevent the ball from coming loose when under load. It can be used on either side of the BulletProof Sway Control Dual Ball Mount. *Does NOT include the dual ball mount