Features:The radiator is also called the passive speaker.It is used to replace the inverted tube.The subwoofer made with the radiator has the following advantages compared with the traditional inverted subwoofer.The low frequency dive depth is equivalent to the backward type, but the speed is the same.The sense is obviously faster than the backward type, occupying advantage of a certain closed box, and at the same for time completely eliminating the drawback of the inverted structure - that is, the wind noise brought by the inverted nozzle. Specifications:Material:Rubber+IronColor:BlackSize:Approx.69.66x58.55mm/2.76x2.32in Note:Please allow 1-2cm errors due to manual measurement,pls make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes:2 x Bass Passive Radiators