Manufactured to conform to US mil spec MIL-A-18001 K composition. Extra narrow anodes to suit limited clearance situations such as between shaft skeg/bearing and propeller boss. Stainless steel socket head cap screws and captured nuts as well as copper rivet pin to ensure secure four point contact to greatly reduce the risk of falling off. S ized to suit imperial prop shaft. Available in zinc or cadmium free aluminium versions.