Martyr zinc gimbal block anode CM43994Z. Replaces Mercury Mercruiser 821631Q 1. New old stock item not in original packaging and soiled from storage. Please note! Unless this item is eligible for Ebay's Global Shipping Program, Skippers Marine only sells and ships to U.S. addresses. If you are an international buyer, please be prepared to supply a U.S. shipping address. Skippers Marine specializes in new old stock marine parts and accessories as well as Sea Ray and Hatteras new and recycled boat parts. Please check out my other Ebay Store items.  Don't see what you are looking for? Feel free to send an email request. 9-8122