The MGDUFF button anode (or disc anode) is a popular zinc anode for use all around your boat from the hull to the trim tabs.  Attach with 10mm bolt or fixing stud. Suitable for saltwater.Sold singularly (one per pack) Specifications Material: Zinc for Saltwater Protection Nominal Weight: 1.0kg Length: 100mm Width: 80mm Depth: 25mm Stud Size: M10 (10mm) Quantity per pack: 1 Number of Fixing Holes: 1 Fixing Hole Details: 11mm Dia