Aluminum Anode For Mercuriser Alpha 1 Gen 1 And Most Mercury Outboard Motors, Replaces Mercury 31640Q 4, Martyr CM31640A, Honda 4110-ZW1-003ZA, Quicksilver 31640A, Tecnoseal 00800AL, Camp 31640AL. This Is A US Military Grade Aluminum Anode Made To The Highest Quality. Made In The USA. Aluminum Is For Sate And Brackish Water Use.