"To achieve the precise control the Atlas truck provides, it was necessary to create a new breed of pivot cup. The Atlas pivot cup is patent-pending technology, like nothing you’ve seen before. This pivot cup is self-cleaning, self-centering, and even threaded so you can remove it with your axle for cleaning and maintenance. The Nylon6 material is a low friction, abrasion resistant material perfectly suited to this type of application. Ships in a set of (2) pivot cups. "
-Atlas Truck Co.