Pre-Owned Rock-Fabrik Effects Aqualung.

A great low gain overdrive that has a super clear, transparent tone with just enough controls to let you dial in a great tone from any guitar with any pickup.

From the manufacturer:

Aqua Lung is a transparent overdrive pedal which has special features such as low-cut and high-cut switches. Also it is overly suitable for clean boost. It can be used as mid boost by cutting low and high frequencies with switches.
Low cut switch clips under 750hz to provide option between bodied and juicy sound. High cut switch clips upper 1,2 khz to defeat harsh sound for humbuckers and also provide burst sound for single pickups without cut. This feature is specially designed for neck pickup of strat.
Aqua Lung is designed to make fine control possible for break up point of tone. It can work with 18V power supply for more headroom and 18V power supply enlarges range around break up point of tone.