From Xotic:

For ultimate swells and control the Xotic Volume Pedal uses high quality audio potentiometers to retain your tone throughout the entire frequency spectrum.

The nylon pivot bushing and rack pinion design creates a super smooth volume sweep under your feet and is highly durable unlike conventional volume pedals designed with string that are prone to snapping and breakdowns.

Available in 250K High Impedance (gold casing)
Xotic Effects Volume Pedal High Impedance 250K Features:

Gold Metallic Aluminum case
High quality audio potentiometer
100% hand wired with cloth covered wire
Nylon pivot bushing
Compact size
Tuner out