Z Guard Aluminium Hull Anode Bolt On – 2 KGS NOM NET WEIGHT 200 MM BOLT CENTRES Sold in single quantities. Box size: 10 Since 1977 Z-Guard has manufactured sacrificial anodes for the major UK boat builders, lifesaving organisations and other recognised trusted UK brands.  Z-Guard has an unrivalled proven pedigree, DNV-GL certified & produce to military specifications Mil-A-18001K, Mil-A-24779 & Mil-A-21412A.