Weber MicroMass Attenuator - 15 Watt 15 watt rating 8 ohms. May be used on 4, 8, and 16 ohm amplifiers Includes MASS bypass, and line out Two power level controls, one for the bass-mid frequencies and one for the upper mids-treble frequencies The attenuation is continuously adjustable from zero to over -50db using the attenuation controls