In the past, the major manufacturers of metal building insulation posted and advertised the density of the fiberglass they produced. This is no longer done. The labels that the manufacturers adhere to their rolls of insulation give the R-value, the thickness, the width, and the length of the product, but do not mention the density. That is because the density is now considered proprietary information due to the fact that the manufacturers adjust the density to achieve the desired R-value, which is what they sell. R-values. The resultant R-value that is posted on the label of the insulation is achieved by adjusting the density. The bottom line is that the fiberglass manufacturers are not selling density and they are not selling thickness; they are selling R-value.