Galvanized steel insert with holes for bolt-on installation - 5/8" holes on 6" centers.
These anodes are built around a high-strength slotted steel mounting insert.
Unlike some competing brands, the steel insert in Sea Shield anodes is galvanized for longer shelf-life and better grounding.
1-1/2" countersunk holes
Built to military specification MIL-A-18001
Made in California, USA