Fluoron, Inc. manufactures Carreras Bushings that are designed to protect today's very expensive synthetic mooring lines from chafing or damage. Such wear on lines increases the possibility of breaking and the "Snap Back Phenomenon" which occurs when a line breaks under extreme tension. These lines are deadly to crew on the ship or dock.
These are made up of a series of rollers that are sized to fit the diameter of the mooring line. They are made with ultra high molecular weight polyethylene (UHMW-PE), the toughest and most wear resistant of all plastics and rubber materials. Other advantages of UHMW-PE are it stays clean and resists ice adhesion.
Video of Carreras Bushings at work