It's a much, much smaller than the ST-1 at only 3.9" wide x 4" deep, and more intelligent version of the epic Supa-Trem1. Sporting True-Bypass,Tap-Tempo, external Tap jack, Half/Double hold feature, up to 15dB boost, true Square, Sine, and the natural heartbeat-like Warble wave-forms! It also can do speeds so slow that a full cycle takes around 10 seconds, and fast speeds beyond 220bpm. The heart of the ST-1 is still there, the warm Analog Devices JFET preamp. And this pedal is so small it will fit in your pocket, and with its top-mounted jacks, will fit in any little spot on your board. Don't forget, just like the ST-1, the Jr also works as an incredible clean boost with the Mix control turned down!