You are looking at the Tone Corset analog compressor by Electro Harmonix.

The Tone Corset, Electro Harmonix's new four-knob analog compressor, squeezes your guitar tone in all the right ways!

The 4-knob design provides excellent control and gives the user the ability to precisely shape their instrument’s dynamics. The Sustain knob controls the amount of compression applied to the guitar signal. The Attack know adjusts how quickly the compressor recovers. As Attack is turned clockwise the pedal’s response is slower and more initial pick attack comes thru. The Blend knob adjusts the mix of the dry and compressed signals. Volume controls the overall output level. The Pad switch pads down the input signal to prevent undesirable distortion if the Tone Coret is used with high output humbuckers, bass guitar, etc. True Bypass for maximum signal path integrity. Comes with a 9V battery.

Features Four-knob design
Sustain, Attack, Blend and Volume controls
Pad switch pads down the input signal
True Bypass
includes 9V battery