GIK Acoustics engineers and builds some of the best acoustic treatments for studios, home studios, home theaters, etc. They use sustainable materials, too.
These are white 7.5" deep "Monster Traps" in white. All are in great condition, but some need a little cleaning. Painters Tape is the recommended cleaning method to remove dirt and smudges. Just press it on and peel it off. The absorption curve is solid down to 70Hz. Check them out at GIKAcoustics.com.
I have various sixes:
4 of the 7.5" x 24" x 48" Monster Traps = $60 each (they cost $120 each new)
4 of the 7.5" x 24" x 48" Monster Traps with internal Scatter Plate Diffusors = $75 each (they cost $150+ new)
2 of the 7.5" x 12" x 47" Monster Traps = $40 each (they cost $80 new)
1 of the 9.5" x 12" x 47" Traps that is a little out of square = Free