This is two popular "cloned" circuits in one box: channel A (right side, input) in a reproduction of the classic RAT V2 LM308N distortion, channel B (left side, output) is a repro of the late 70's "gray spec" DOD OD-250 overdrive ("the Yngwie favorite"). Use them individually or chained - many, many tone/boost combos possible. Fantastic chunky drive when chained together. Both circuits are properly isolated and filtered, resulting in a "stacked" pedal that's much quieter than chaining together separate pedals. Internal battery clip for power, although use of a single high quality "Boss style" external 9v "center negative" adapter is recommended.
SOUND CLIPS HERE (clean, then Rat only, then 250 only, then stacked):
https://soundcloud.com/mikepo/rat-gray-spec-combo