Auralex Acoustics LENCHA LENRD Acoustic Absorption Bass Traps, 24" x 12" x 12", 8 Pack, Charcoal LENRD stands for Low-End Node Reduction Device Helps to Control the Low Frequency Response Of Your Space Designed for corner mounting between walls and ceilings, can also be wall-mounted horizontally Each LENRD is 12" x 12" x 24" (2 Linear Feet of Absorption) Effective absorption down to 63Hz with NRC (Noise Reduction coefficient ) 1.50