Fully automatic and self-centering dual cam sway control works to control trailer sway before it starts rather than just resisting sway once it�s begun. And it works only when needed! Cams on either side of the trailer lock in position when towing in a straight line to minimize sway caused by high crosswinds or passing vehicles. Another advantage of the dual cam system is that it�s installed on the trailer so doesn�t require adjustment every time the towing vehicle and trailer are hooked up. Weight distributing hitch is not included. Use with surge brakes is not recommended. 1 per box.