Mercruiser Merc Alpha One Outdrive Lower Trim Tab Fin Zinc Anode 31640 Mil-Spec USA Mercruiser Merc Alpha One Outdrive Lower Trim Tab Fin Zinc Anode Replaces: 31640Q4 , 31640 4 , 31640 3 , 31640A 1 , 31640 , 31640A 2 , 72436A1 Brand new replacement trim tab anode for Mercruiser Alpha One sterndrives and many Mercury Outboards Mil Spec Hand Poured, Made in the USA Ships Priority Mail in the USA for 1-3 day Delivery