The ZOOM B1 FOUR and B1X FOUR bass multi-effects processors deliver over 70 effects and amp models, a built-in looper, 68 rhythm patterns, and nine classic amp simulations. The B1X FOUR adds an expression pedal for hands-on control, while both units allow storing 50 custom patches, silent preselection, and accurate tuning. Compact and lightweight, they support active and passive basses, feature USB and auxiliary connections, and run on AA batteries for up to 18 hours of use.