My supplier for acoustical cotton just informed me that they had a manufacturing SNAFU. While making a batch of the 4" BAC, they put in too much bonding agent. This results in the material only being approx 3" thick. The amount of cotton is still the same so the density will be increased approx 33%.
The price has been reduced if you're interested in these 'factory seconds' by approx 25%. Contact me if you're interested. As of this afternoon- there were a couple hundred pieces left. When they're gone, they're gone.