The Max-Prop Anode has a metal ring molded into it. This metal ring goes around the entire diameter where the screws attach the Anode to the propeller. This ring disburses the electrical current through the entire Anode giving it a much longer life.
Even with the metal ring PYI recommends when installing the zinc that you clean the flat surface of the zinc and the back of the propeller so that you will have good contact between the zinc and the prop. This will greatly increase the life of the Anode.
PYI sells only Mil Spec Anodes. Individual Anodes do not come with screws.