High-Density -Retardant Material: The sound absorbing foam panels is made of -retardant and environmentally materials, which can be used safely. The absorption spectrum is wide and over 500 HZ.High-Density material,which is higher than the industry standard of 30%. At the time, it can also sound quality: by absorbing harmful sounds, reducing fluctuations, reverberation, and vibrating , Useful sounds are clearer. The principle of the soundproofing foam is the sound inside the sponge is repeatedly reflected back and forth, thereby achieving the effect of noise reduction and sound absorption.the acoustic panels not only have effective sound absorption characteristics, but also will not any harm to our body.The high quality material studio foam can keep sound insulation function permanently. In terms of cleaning, you just need to vacuum and dust occasionally. How To The Normal Size Of The Acoustic Foam: 1. After opening the Vacuum package, place the Acoustic Foam in a ventilated place for 12-24 hours; 2. Or soak the foam in water for 1 minute, wring it dry, then dry or a blower dry. Installation : It is recommended to stick the tape to the four corners and the center of the back of the acoustic foam panels, and then to the wall. Or you can purchase spray glue to install the soundproofing foam according to your needs. For professional acoustic control Acoustic Foam Each comes uncompressed and in prime condition! With professional acoustic control, sound suppression, acoustic proce. size:30x30x2.5cm Material:Polyurethane colour:Black+red Package Contents: 24 * black sound-absorbing cotton 24 * Red sound-absorbing cotton Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.