McCaffrey Audio Reactor Boost Compressor Guitar Pedal Fusion: Affects the amount of compression and drive when the level is increased Enhances your overall tone. You'll never want to turn it off Level: Increases/decreases output volume of pedal. Increase the level and notice how the pedal starts to push the front end of your amp and other pedals Critical Mass Switch: Three-way switch that adds bass response to the effect. Middle is the stock or jangle position. Adds a bit O snap to pickn. Left adds just a bit more bass response. Right adds the most bass response Compression and Boost in one uniquely designed pedal