The Used Keeley 4 Knob Compressor is a boutique-quality effects pedal known for its studio-grade compression and exceptional sustain, ideal for guitarists seeking dynamic control and tonal enhancement. This unit is in good condition with only light cosmetic wear and functions perfectly. It features four control knobs��Sustain, Level, Attack, and Clipping��for precise adjustment of compression intensity and tone shaping. Built in the USA, it utilizes high-quality components and true bypass switching to preserve your signal integrity. Its transparent compression makes it perfect for both subtle leveling and squashed, punchy tones. Powered by a standard 9V DC power supply (not included) or 9V battery, this pedal is a must-have for guitarists looking to elevate their sound with clarity and sustain.