Springfield Marine Taper Lock Deck Base 9" Flat. It is constructed of high-strength aluminum to withstand all conditions. Use with any Taper-Lock Post (sold separately). Features of Springfield Marine 1600005 Taper Lock Deck Base 9" Flat Satin finish High-strength aluminum construction Below the deck mount requires a 3-1/2" hole in deck Use with any Taper-Lock Post (sold separately) 9" by 7" flat base with an 8" hole pattern Package Contents: Springfield Marine 1600005 Taper Lock Deck Base 9" Flat Springfield Marine 1600005: Taper Lock Deck Base 9" Flat