Dunlop produced the M250-U MXR Double-Double Overdrive as a dual-circuit overdrive pedal housed in a single enclosure. It occupied a place in the MXR effects line as a versatile overdrive unit, offering two distinct gain voices selectable via a switch rather than requiring a second pedal.

The M250-U carried two independent overdrive circuits: a Low Gain circuit voiced for rich, fiery midrange character, and a High Gain circuit configured to increase gain while emphasising the high and low frequency ranges. Tone controls were provided to further shape the overdriven signal. On the technical side, the pedal presented an input impedance of approximately 1 MΩ at 1 kHz and an output impedance of 100 ohms at 1 kHz, with a maximum gain in excess of 40 dBV and below 50 dBV. The noise floor measured at -90 dBV, and power consumption ran below 14 mA at 9 VDC.

Owners requiring service, internal adjustment, or help sourcing a compatible 9 VDC power supply should consult a qualified guitar technician familiar with effects pedal circuitry.