In the words of Dunlop:

Saving space doesnt mean skimping on durability or functionalitythe

DVP4 Mini Volume (X) Pedal does everything that the larger DVP3 does at

half the size, and its just as durable and solidly built with a

lightweight aluminum chassis, aggressive non-slip tread, and our

patented Low Friction Band-Drive for a smooth range of motion and

consistent, reliable performance. For maximum comfort and precision, the

DVP4s rocker tension is fully adjustable.

The AUX output combines tuner and expression functionality into one jack

that can be toggled with a switch inside the pedal. When using the DVP4

as an expression pedal, you can use an internal pot to set the minimum

level of the parameter youre controlling with the rocker. If you want

to reverse the function of the heel-down and toe-down positions, the

DVP4 has another internal switch that allows you to do so.