Features：

Bass radiator, also known as a "drone cone", for replacing the inverted tube or subwoofer with the radiator and the traditional back subwoofer.
A passive radiator system uses the sound otherwise trapped in the enclosure to excite a resonance that makes it easier for the speaker system to create the deepest pitches
Air turbulence noise is no longer an issue, when air rapidly escapes the pipe at high volumes.No more high frequencies reflected out the port.
Passive radiators operate in conjunction with the active driver at low frequencies, sharing the acoustic load and reduce the excursion of the driver.
Working similarly to a vent, the passive radiator will only add as much as they subtract.

Specification:

Material: Rubber, Iron (metal plate at the middle)
Color: Black
Outer Diameter:32mm
Inner Diameter:20mm
Height:2mm

Package Content：

4 x Speaker Radiator