Maxon OD9 Plus used

This pedal is in very good condition.

From Maxon FX:

In 9-volt setting the Pro+ sounds and functions like the standard OD-9 with the added option of a healthy +3 dB of midrange boost at approximately 800 Hz (actual frequency is dependent on Control settings) – great for cutting through a band during solos.

When set to 18-volts the OD-9 Pro+ becomes an 800-pound Gorilla, offering up beefier lows, tighter saturation, improved dynamics and a chunky, aggressive pick attack that will make your amp sound and feel like it just took a Viagra.  Switch on the Mid Boost in this mode and let your solos breathe fire.