Designed to "clean condition and protect marine vinyl and rubber components.". After 2 seasons of use it seems to be keeping the rubber pliable. It had been close to drying out and cracking before I started using it. It soaks into the rubber and doesn't attract dirt or leave residue. Needless to say, wash off any salt and let dry before applying. You can get it at West or at many other places for about 1/2 what West charges. A small bottle will last many years.