Amp rack panel / 1U high 19 standard. Each has two channels of XLR input / loop through for signal inputs and NL4 for the amplifier / speaker outputs. The XLR signal inputs have a front mounted switch with links the two channels together to make the rack / amplifier mono. The speaker outputs (all soldered) are wired onto pins 1+/1- on their respective channels. The’both output’ NL4’s have the Left Chanel wired to pins 1+/1- and the right channel to pins 2+/2- which allows both amplifier channels to be sent down one 4 core cable. Perfect for small amp racks etc. Used with a few scratches / scuffs / dents / marks etc but in usable condition, please see photos. See my other listings for more audio & related items.