This is a Boss NS-2 Noise Suppressor Pedal. It eliminates unwanted noise and hum in guitar and bass effects and amplifier setups without altering an instrument's natural tone. It's the perfect pedal to quiet down any pedalboard or effects setup. It has a unique noise detection circuit that preserves the natural attack and envelope of an instrument's sound and includes threshold and decay knobs that allow for shaping the elimination/suppression as desired.

This has hardly been used and is in excellent condition.