Avoid snaking when towing use an AM Controller for precise, safe and stable loading of caravans and trailers. The spring is chromium plated steel and the design was carefully calculated by three civil engineers to produce a quality nose weight gauge. It is durable, handy, easy to use and sensibly priced. The patented controller is fixed onto the tow ball of the towing vehicle. Lock it in place by simply turning the red locking ring 1/2" turn. Lower the trailer coupling head onto the top of the controller.