CURT adjustable channel ball mounts are not only built for tough jobs, but they are also engineered to offer smooth, quiet towing. Built into the adjustable shank is an anti rattle mechanism a rubber bumper that goes between the shank channel and the trailer ball attachment. This anti rattle bumper greatly reduces vibrations and noise coming from the coupling point, providing a smoother, quieter ride for the road ahead. In the world of heavy duty towing, harsh conditions and relentless exposure to the elements aren't uncommon. For this reason, the adjustable channel mount is finished with a highly durable carbide black powder coat finish. This helps withstand rain, snow, dirt and road salt, protecting the shank from rust and corrosion.