VETUS shaft anodes are designed to create a perfect fit on the shaft. Even as the anode is eroded, it cannot come loose. An interlock system is incorporated in both halves, to ensure that the bolt holes are in perfect alignment. The material around the holes is also increased to prevent the bolts becoming loose.Shaft anodes are not recommended on high speed vessels. They create turbulence in the water flow around the propeller and as they erode, can cause imbalance in the propeller shaft. These problems do not occur when using the VETUS propeller nut with integrated zinc anode.