I am selling these because I bought them but never used them. These are 30cm x 30cm, 9mm thick sound-absorbing panels. Quantity: 36 panels Main Specifications: 【Sound Absorption Effect Improved by Approximately 2.5 Times】 The sound absorption effect of sound-absorbing materials is determined by the density of the board material. The higher the density, the better the sound absorption and soundproofing effect. By increasing the density of the board material to approximately 200kg/m³, the sound absorption effect has reached approximately 2.5 times that of other companies' products. You can enjoy high-quality, clear audio. 【Carefully Selected Materials】 YOPIN sound-absorbing boards are made of environmentally friendly, flame-retardant, high-quality polyester fiber, which is odorless and not only has excellent sound absorption but can also be used as insulation. It improves the efficiency of air conditioning and achieves energy-saving effects. They are delivered without compression, so they can be used immediately. 【Wide Range of Applications】 The sound-absorbing panels come with insect pins for installation and can be easily installed on walls, doors, and ceilings. Because they use insect pins, you can remove them without damaging the walls. They are widely used in bedrooms, piano practice rooms, recording rooms, offices, conference rooms, etc. 【Advice】 To obtain the ideal sound absorption effect, it is recommended that the sound-absorbing sheets cover more than 70% of the walls of the room. Also, if you are pursuing a better sound absorption effect, we recommend using them in conjunction with YOPIN soundproofing materials.