This is a case of 2' x 4' x 1" thick Owens Corning Thermafiber mineral wool. The 8 pound per cubic foot density both insulates well and absorbs sound better than lower density mineral wools. Can be easily cut with a knife or serrated blade and will compress to fit in to gaps. Thermafiber is a dense insulation batt that needs to be supported for overhead applications. It is commonly used for exterior walls as well as for sound deadening within interior walls and ceilings. Similar to Rockwool and other mineral wools.