The Red Square combines two of Jetter's overdrive pedals - the Red Shift and the Helium - into a single enclosure. There's an internal switch to set which of the two comes first in the signal chain.
The Red Shift side offers two different voicings courtesy of the shift switch and sports volume, gain and tone knobs, while the Helium side offers volume and drive plus the lean/rich knob for tonal tweaks.
What you get from both aspects is a natural amp-like overdrive - the Helium side offering a Fenderish flavour with a useful range of those low-gain just-breaking-up tones, while the Red side has more gain and a nice fat sustain that turns more aggressively Marshall-like with the shift switch.
The two sides complement each other really well (which is the whole point of putting them together) giving you plenty of tonal variation and, with two footswitches, a choice of how you utilise the pedal.
Two distinctly different overdrives used separately or together, or one main overdrive with the other set to just boost it when needed? The choice is yours.
This is one really versatile and great-sounding overdrive pedal. In our recent review of the whole Jetter range, the Red Shift and Helium emerged as our favourites - putting both together in a single box at a price much less than buying the individual pedals is a no-brainer. Excellent.