Great effects pedals. Very flexible and gives you tons of sounds. They are essentially idetical with the difference being the B2.1u has the expression pedal buil in and has a USB audio interface as well. Included with each is a Boss FS-5U pedal that you can assign to bypass/mute the units or other funtions like drum machine start/stop, delay hold, tap tempo. Both units have Velcro on the bottom for easy pedal board mounting. Both ship in original boxes with manuals. B2.1u $80 shipped B2 $60 shipped PayPal accepted. PM me with any questions.