Here's what Dunlop say about the DVP5 Volume (X)8 Pedal:

The Volume (X)8 Pedal features an 8" housing to give you the most efficient use of your pedalboard space.

Designed with our friends at Pedaltrain®, the Volume (X)8 Pedal allows for the most efficient layouts on Metro Series and other popular pedalboards. Once you're all set up, step on this pedal to create incredibly smooth volume swells or control your favorite FX parameters with the road-proven, patented Low Friction Band-Drive. Internal controls set the expression mode’s minimum effect level parameters and the rocker's heel/toe polarity. Features Volume, FX, Output, and Tuner jacks.