In any air suspension system, you will have air springs that take the place of your factory suspension. When deflating your air springs, you will hear an audible release of the air from the springs or bags. While many find this sound very pleasing, others may not. If you are wanting the quietest operation possible from your air springs, you can use the AccuAir PTC mufflers to help keep things quiet. These PTC mufflers simply press into each end of the VU4 to significantly reduce the exhaust noise. This helps to muffle the sound of the air being released and give you an overall quieter operation when airing out or deflating your springs.