The Electro-Harmonix Soul Preacher Compressor Sustainer Guitar Effect Pedal is a versatile and high-quality guitar effect pedal. It offers both compression and sustainer features, allowing guitarists to create dynamic and expressive sounds. The Soul Preacher model is specifically crafted to enhance and sustain the tone of your electric guitar. It has also three way toggle switch FAST MED SLOW. Because its unique design and extra features I found it to be more useful in compression than MXR Dyna Comp or BOSS Compressors.