Streamlined collars are made to fit tightly around the entire propeller shaft. Water between the collar and shaft can lead to the anode degrading from the inside which causes it to loosen and spin, losing all metal contact and becoming useless. Other manufacturers may use small BB’s to make up for a poor fit. This lifts the collar off the driveshaft creating the same effect. Insist only on ElectroGuard anodes and ensure a proper fit! The nuts on all our collars are also staked into the anode so they will not fall out during installation.