Deadening Sheets (Vibration Dampening Material) Approximately 10cm x Approximately 4.5cm x Approximately 2.5mm, 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 them 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'm waiting for your questions.