I8D4 - Incriminator Audio 8" Dual 4-Ohm Subwoofer (I-8D4) I8D4 - Incriminator Audio 8" Dual 4-Ohm Subwoofer Outer Diameter: 8 1/2" Mounting Diameter: 7 15/16" Mounting Depth: 4 1/16" Displacement: .10 cu. ft.