This is Owens Corning 703 rigid fiberglass board in a case of 6 24 x 48 x 2 inch pieces.
Owens Corning 703 is probably the most popular material for acoustic absorption. It is typically covered with fabric and mounted on the walls in a studio, control room, or listening room.
Click for Owens Corning 703 single pieces.
For an identical product at a lower price, check out ATS Acoustics Rigid Fiberglass Board. The name and the price are the only differences.