I have six Sonance Acoustic Pillows for sale. These are for inwall speaker installations. Two are used per speaker - enough to treat the front left, right, and center inwall speakers. $60 per Acoustic Pillow set or $30 each.
SonaFill improves the performance of in-wall speakers - . absorptive pillows absorb sound within the wall cavity. Can be used in new construction as well as retrofit installations.
http://www.sonance.com/products/accessories/detail/228
