Planet Audio AC8D 1200 Watt, 8 Inch, Dual 4 Ohm Voice Coil Car Subwoofer CONE: Made From Polypropylene, The AC8D 8 Inch Car Subwoofer Provides a Resilient And Durable Material That Can Offer Great Sound With The Advantage Of Long Lasting Subwoofers VOICE COIL: Our Voice Coils Are Able To Withstand High Temperatures Yet Maintain Its Strength And Fatigue Properties. Making Our Voice Coils With This Material, Gives Our Speakers The Advantage Of Longer Pay Times With Lower Weights SURROUND: Foam is very flexible, providing the subwoofer with higher efficiency. This also translates to better excursion. (How far the cone of a speaker linearly travels from its resting position). STAMPED BASKET: A Die-cast frame can absorb and transfer much of the energy produced by the speaker. It has good corrosion resistance, good mechanical property, high thermal and electrical conductivity and retains strength at high temperatures. SPECIFICATIONS: Resonant Frequency - 39 Hz, Sensitivity SPL (1W/1m) - 85 Db DIMENSIONS: Depth 9 x Width 9 x Height 4.5 WARRANTY: Planet Audio Provides a Powerful 3 Year Platinum Online Dealer Warranty So Long as The Purchase Is Made Through Amazon.com