Auralex - 1 Inch Studiofoam Wedge (Burgundy)

The 1" Studiofoam Wedge works most effectively on mid and high frequency sound waves and may be used to acoustically treat walls or, most commonly ceilings (especially if they aren't parallel to the floor,) even when the walls are treated with thicker acoustic Studiofoam.
Anechoic wedge cut offers superior sound absorption
Works most effectively on mid and high frequency sound waves
Consistency of cut minimizes visible seams