I had bought this pedal a little over a year back & have just recently taken the time to sit down, tweak, & utilize it within my bass rig/fx.
I've never been much a fan for big muff circuit on bass. Having had the OP amp version built for me (mainly for guitar) it sounds alright on bass, but not what i would go for entirely. Played various types of fuzz & nothing really sounded right (again, am more overdrive/distortion than fuzz on bass). Found this at a small local shop for next to nothing & had to swipe it up, & once back, playing my then gf's active squier dimension bass it sounded good. I was able to tweak the internal controls to give a more open tone. Fast forward to now, while building/reconfiguring my new bigger bass board, i felt i wanted to try to utilize the pickle & i spent more time tweaking the internal controls (Clip & Voice) to my liking, & then set the filter & sustain, followed by the scoop & crunch controls. The key to having this pedal work on bass is determined where you set the internal controls (& with which fx before/after it affect it). I run mine after an MXR 10 band EQ (which is set with a low mid cut & mid boost to cut through while not boosting/bloating gain), & right before an mxr bass d.i.+ (which serves as my low gain drive). Since my clean bass tone is pretty midrange heavy (Old school punk oriented music with some hints of other genres), i wanted the swollen pickle to retain that midrange but have its nice fuzzy tone. It has significant volume on tap, & personal taste - i keep the sustain low around 9 oclock. Its just enough fuzz to rumble.
It's built solid, works like a charm, i give it 4.5 due to it needing more time spent to find a usuable tone for ones sound because every control is very interactive. It's not for everyone, but if you're looking for a green/black russian muff variant, with a little more flexibility - this is a good alternative.