Surround – Butyl RubberView larger Surround – Butyl Rubber Butyl Rubber is a synthetic (man made) material and is valued for its chemical inertness, impermeability to air, and ability to endure or resist exposure to the many types of weather fronts. Butyl rubber applications from sports equipment to automotive parts, the medical industry and more.It is used in the Surrounds that connect the cone to the basket. Did you know that most modern chewing gum uses food-grade butyl rubber as the central gum base, which contributes not only the gum's elasticity but an obstinate, sticky quality? Just like that chewing gum, the Butyl Rubber Surround in our speakers can take the equivalent amount of abuse without quitting on you. Specifications 12 inch 1000 Watt Dual Voice Coil SubwooferPower Handling (Peak): 1000WPower Handling (Continuous): 500WSensitivity (1 Watt/1 Meter): 95dBImpedance: Dual 4 OhmVoice Coil: 2-1/2 inchMounting Depth: 6-3/16"Frequency Response: 12 Hz – 350 Hz Voice Coil – AluminumView larger Voice Coil – Aluminum Our speakers are capable of higher or elevated temperature strength and fatigue properties that will increase performance and efficiency of heavy duty play time through lower weight and higher operating temperatures. Cone – Poly InjectionView larger Cone – Poly Injection Polyurethane is a resilient, flexible and durable manufactured material that can take the place of paint, cotton, rubber, metal, or wood in thousands of applications across virtually all fields. It can be hard like fiberglass, squishy like upholstery foam, protective like varnish, bouncy like rubber, or sticky like glue. In the specific case of our cones, this material allows for maximum flexibility that produces great sounding speakers lasting you a long, long time.