All universal Alpine earplugs are fitted with AlpineAcousticFilters. Whereas foam earplugs fully block all sounds, the AlpineAcousticFilters allow the sounds to be filtered. Because of this, the AAF absorb annoying sounds, while still allowing you to hear the other sounds. Thanks to an extremely accurate production process and very tight tolerances every earplug with filter has the perfect absorption for the specific use. The specific absorption value of the filter is indicated with every product.
Since you don’t want to be completely disconnected from your surroundings, these special filters have an open system. Because of this, the filters prevent a tight sensation or the sensation of being disconnected from one’s surroundings.