Not so-well hidden secret about this pedal is that is a 100% clone of famous Fulltone OCD Obsessive Compulsive Drive pedal (version 1). I bought this pedal on a whim, you can find at 30 EUR / USD easily on several web shops. I did not have much expectations, but I ended up liking it a lot even though the pedal looks a bit… cheap with a stock skull-type graphics.
This pedal has middle to low-high distortion sound, which should suit rock and classic metal style of guitarists well. Very simple settings: gain, tone and volume + hi/low switch for gain if you need a just little more kick. Personally I use this as booster pedal to already overdriven tube amp. I like to crank the volume knob, minimize gain and roll back the tone just a touch to lessen harshness. This should work well as a distortion source for Fender-type clean amps. There is also true-bypass which is very nice.
For a cheap replica pedal the case and knobs on JF-02 Ultimate Overdrive are very sturdy. On/off switch feels a bit stiff at first, but it has worked fine. Very good bang for the buck. But I end up this review with reminder that it is important to remember the original which is the Fulltone OCD – pedal. Buy the original if money is not a issue and you want to support the original designers! And OCD looks much cooler too on your pedal board :)