Well, NRC is a measure of the absorption value averaged at four frequencies. NRC (NOISE REDUCTION COEFFICIENT): The measure of the acoustical absorption performance of a material, calculated by averaging its sound absorption coefficients at 250, 500, 1000 and 2000 Hz, expressed to the nearest multiple of 0.05. The foam is class B flame retardant. The foambymail.com site does post this for the different styles of foam, it's just not under every product....but it's there. I ordered the 2" wedge tiles....I'll let you all know what I think of them when they arrive. Thanks.
Stan