Deadening Sheets (Vibration Dampening Material) Approximately 10cm x Approximately 4.5cm, Approximately 2.5mm thick, 20 sheets Applying 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 16 sheets (8 sheets x 2 doors) for the inside of the doors. You can also create an environment where you can listen purely to the sound from the speakers. I actually use these in my own car as shown in the photos, and I feel a change in the weight of the doors, a sense of solidity, and a change in the acoustics. I welcome any questions.