Juan Alderete, bassist with Zavalaz (previously with The Mars Volta) came by our booth at 2013 Summer NAMM and checked out the FatRock on bass. He was impressed. The tone changes we made to go from the normal TightRock to the FatRock are similar to the changes used to create the Bass TightDrive from the guitar version....so naturally this one works great for bass if you need a higher gain tone. For more info go to amptweaker.com