ALUMINIUM DECK PLATES.Aluminium alloy deck plates complete with rubber "O" ring and key. Ideal for aluminium boats for survey requirements. For weld-on or for fastening - has pilot holes drilled under the top plate. 2 sizes available 100mm-4" or 150mm 6" inside hole size. Supplied with key.,Inside Hole: 147mm,O/All Dia: 208mm,Cut Out: 160mm .