Gallien Krueger GK 400RB Mark IV Bass HeadNotes Top enclosure not included. Excellent condition otherwise. A Gallien Krueger GK 400RB Mark IV Bass Head in Excellent condition! At Evolution Music, we attempt to highlight cosmetic defects (if any) by picturing every angle of every piece of gear so you know exactly what you are getting. We always picture any and all accessories too. What you see is what you will get so please check out the pictures! Everything we sell has been tested and is