Fatter, louder tones with single-coil pickups; ultra-fat tone when used with humbuckers!
The EMG SPC or "Strat Presence Control" is a presence control knob that is often called the fat control. The original intent of the SPC was to turn the tone of a single-coil pickup into that of a dual-coil. This is accomplished by boosting the gain in a broad mid-band fashion and reducing the highs. The result is a fatter, louder tone from any single coil pickup, but you can also use the EMG SPC on a humbucker pickup to give you a high output, really fat tone that's great for slide guitar.
EMG includes an output jack and battery clip set with the SPC control knob.