It comes complete with a 10mm diameter mounting bracket. Whether your boat is steel or GRP, to provide the best protection to the stern gear the shaft should be fitted with an MGDUFF Electro Eliminator Brush assembly. The MGDUFF Electro-Eliminators offer the most effective shaft bonding solution. Running directly onto the propeller shaft the electro eliminator puts the anode in constant low resistance contact with the propeller shaft. The copper graphite brushes will give at least 2000 running hours under normal conditions. The electro eliminators will also remove the interference to electronic equipment caused by the rotating shaft.