It's their expression pedal that's designed specifically for the H9, and it works well. I rarely use a volume pedal, but I have an Xotic I use alongside the pedalboard on those rare occasions I need one (though I believe that the H9s can be programmed to react to expression pedal changes as volume on a patch by patch basis, which seems like a very long run for a short slide!).Nice board you got there. How do you like the sweep of the Mission Engineering pedal? Is it an expression or volume pedal?