Yanmar Split Ring Sail Drive Zinc Anode (YSD-1) Yanmar Split Ring Sail Drive Zinc Anode For Yanmar SD20, SD30, SD31, SD40 and SD50 saildrives. Pair of split ring anodes use with an adapter plate that enables anode replacement without prop removal. Fits Yanmar Sail Drive Models: SD 20, SD 30, SD 31, SD 40 & SD 50 All anodes are built to high quality standards and meet United States Military specifications. Tecnoseal's in-house laboratory facilities ensure the purity of the raw material and that the composition of the alloy in the finished product meets internationally accepted standards, including the United States Military specifications. The molds are designed using three-dimensional CAD and manufactured with CNC machines. The die-cast molding method is extremely accurate due to the high quality injection process machinery. Finishing and quality control of the final product is still done by hand. Zinc Is For Salt Water Use!