Deadening Sheet (Vibration Dampening Material) 20 sheets Approximately 10cm x Approximately 4.5cm x Approximately 2.5mm Applying it to the back of speakers, inside doors, and the trunk room can prevent surrounding rattling noises and road noise from outside the car. I personally recommend 32 sheets (8 sheets x 4 doors) for the door interiors. You can also create an environment where you can listen purely to the sound from the speakers. I actually use it in my own car as shown in the photos, and I feel the change in the weight of the doors, the sense of weightiness, and the improvement in sound quality. Feel free to ask any questions.