Walkers Ultimate Power Muff Quads Electronic Shooting Ear Muffs are truly extraordinary. Walkers Ultimate Power Muff Quads include a high 27 NRR, an advanced sound compression amplifier that raises the volume of low sounds up to 9 times normal while simultaneously limiting the volume of dangerously loud sounds, and a 4-speaker surround sound for optimal situational awareness. As a result, you hear everything around you, clearly, comfortably and safely.