[ Design of Wedge ] wedge design increases the contact area with sound. Performs good in absorbing and eliminating unwanted echoes, flutter echoes, standing waves, reverb. You can harness to create the optimal environment for music recording or peaceful work. [Fast Expansion] What makes our acoustic foam panels is their quick expansion even after they stay in compressed sealed package for a long time. Usually they puff up immediately when you open the bag, but sometimes may take a bit longer from a few hours to days due to other factors affection. [Flame Retardant Material] Our acoustic foam panels are designed with professional-grade open cell polyurethane foam, passed the environmental protection and flame retardancy test of SGS, for safe and comfortable use. [Widely Usage] acoustic soundproofing foam wedges can be used in any room that requires acoustic control or better music recording, perfect for recording studios, vocal rooms, control rooms, and perfect for home theaters, professional cinemas, concert , and more. with adhesive backing, the color is random, no designation is accepted Colour:Black Material:Polyurethane Size:about 30x30x5cm Package Contents: 12 x Acoustic Foam Panels Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.