Springfield Marine Co 9 X 7-Inch Taperlock Deck Base Number: 7025279" Flat Side Base With 82 Hole Pattern, High-Strength Aluminum To Withstand All Conditions. Below The Deck Mount Requires A 3-1/2" Hole In Deck. Base diameter: 9" Material: Aluminium Pin diameter: 3 1/2" Number: 7025279" Flat Side Base With 82 Hole Pattern, High-Strength Aluminum To Withstand All Conditions. Below The Deck Mount Requires A 3-1/2" Hole In Deck.