It's primarily a boost pedal tailored specifically for bass. It's also got an internal trim pot that can dial in more or less dirt to your signal (I currently have it set completely clean).
These are the frequency ranges I ordered based on one that Peter was already building: 15Hz to 1.5kHz for the Tight control with most of the sweep in the 40Hz-200Hz cutoff range and 320Hz up to zero cut for the Smooth control (standard specs are 70Hz to 1.5kHz and 320Hz to 7.2kHz).