Excellent condition EHX Double Muff! Blend 2 fuzz circuits for a plethora of overdrive and fuzz tones, with a wide range of gain options! Save space on your board by owning a 2 in 1 overdrive and fuzz pedal ;) Here's what Electro Harmonix have to say about it:

The original 1969 plug-in Muff Fuzz had just a touch of overdrive and sounded like a vintage amp with a slightly torn speaker. We paired two of these together in one box to create the EHX Double Muff Fuzz/Overdrive. Use just one Muff for a hint of milky distortion, or cascade the second Muff for over-the-top overdrive that turns the milk into cream. Two distortions in one compact package.