RE Audio REX10D4 10-Inch Dual 4 Ohm Voice Coil Woofer Mica Filled Poly Cone, Santoprene Rubber Surround Pressed Steel Basket, High Temp 8-layer Copper Voice Coil FEA-optimized Motor Structure, Single Magnet Linear Conex Spiders, Rubber Gasket Nominal Impedance: Dual 4 Ohm, Power Handling: 175W (RMS)