The Ernie Ball Expression Overdrive pedal gives you sweepable control over the amount of gain and boost, from totally clean through mild breakup and aggressive drive. The rotary control side of the pedal lets you dial in max amounts for drive, tone and boost, then the sweepable expression pedal goes from all the way off at the heel to the edge of your set controls. Use this versatile pedal to change up overdrive sounds from one section of a song to another, or have a crunch tone that can be taken into a higher gain solo sound by inching it up to taste.