Rockwool Acoustic Mineral Wool Insulation 40LT - 4lb 48"x24"x2" 6pcs Mineral Wool Insulation in 4lbs per unit density. Great as Acoustic insulation or as a soundproofing material Cost effective and Very High NRC Rating, better than Owens Corning 703 Water repelling - hydrophobic- Class A fire rating Rigid Boards, perfect for making acoustic panels and bass traps