If you own multiple trailers or frequently tow a variety of loads, you know how much time and money are spent tailoring your towing system to each and every individual trailer. There is nothing more inconvenient than switching back and forth between a few different ball mounts and trying to remember which mount fits with which trailer. A Curt Manufacturing adjustable ball mount is your multipurpose towing solution. Its key feature is its adjustable design that takes the form of an adjustable channel-style assembly. It uses a series of holes to allow the ball mount platform to be vertically adjusted and allow for significant flexibility in drop and rise. With a variable ball height, it can easily accommodate different coupler heights and multiple trailers.This replacement anti-rattle kit is designed to fit Curt Manufacturing adjustable channel mounts #45900 and 45901. It threads into the back of the channel mount and tightens to reduce vibrations.