RE Audio MX18D1 18-Inch Dual Composite 2 Piece Cone with 1 Ohm Performance Woofer Dual Composite 2-piece Cone, Ultra Rubber Surround Cast Aluminum Basket, Tork-Tite Terminal 4" 4-layer Aluminum Voice Coil, FEA-optimized Motor Structure Powerful "Neo" Magnet, Dual Progressive Spiders Dual 1 Ohm Voice Coil