All pedals are hand painted and hand assembled, and each is unique. The pedal you purchase may vary in appearance from this stock photo.
The Double Rock by ZVEX was originally designed for J. Mascis of Dinosaur Jr. He requested two Box of Rock pedals in one box with two stomp switches. He uses that regularly on stage now, but ZVex did one better with the one they're releasing to the public...They made it so you can adjust the sub frequencies (like the Distortron), and you can convert either channel to a Super Hard-On. In this way, you can configure the pedal to be two Distortions cascaded, two Super Hard-Ons cascaded, or a Box of Rock with boost, or a Super Hard-On going into a Box of Rock.
ZVex recommends putting the Double Rock last in your pedal chain and setting your amp to your favorite clean tone and set the Double Rock to your favorite distortion/boost tones.