The LENRD in these Auralex Acoustic panels stands for Low-end Node Reduction Device – and they’re meant to spearhead room nodes, or resonance bumps in particular room frequencies. Using LENRD panels, you can experience much more accurate low frequency reproduction, with an ultra-simple installation. The Auralex LENRD panels fit comfortably in your room’s corners and attach to the wall easily. This is a 4-pack of Auralex acoustic LENRD panels. Plus, to best suit your live or control room’s decor, Auralex offers LENRD panels in charcoal, purple, and burgundy.