For years I used Rat distortion boxes for guitar and for bass. Now I play bass a lot more in bands, and find the Rat sound to be weak and one dimensional. I sold off my rat and tried out a number of other distortion boxes at a local shop and settled on the Big Muff Pi. This thing is rich. The complexity of the distortion is incredible compared to what you get with most other pedals--must be the brilliant Russian engineering behind it. It has three knobs: Volume, Sustain, and Tone. The Volume is obvious, the sustain is really the distortion level. For the Bass, I run the sustain very low, and the volume higher and get a great mix of clean and distorted tone. Sometimes I run the sustain knob turned all the way off and this thing still drives the sound nicely. Too much distortion on the bass and you loose your ability to cut through the rest of the band in my opinion. The Tone knob adjusts the center frequency of the distortion. I run mine way over to the left and distort the low end around 200-400 kHz. You can crank it around and get anything from a low grumbly distortion tall the way to a really tinny irritating heavy metal sound. This thing is versatile, and no matter how you like your settings, the distortion it produces is rich in harmonic overtones, multi-dimensional, and unlike any other boxes I've tried. Highly recommended.