Hi, after installing the MNPSB into my MNSOB3R-4P I'd like to suggest that people with fat short fingers will probably find it easier to connect the wires to the unit before mounting it down on the standoffs, and some mention that the power for the PSB should come from the switched side so it de-energizes when tripped would probably help. The description makes it sound as though it is only compatible with transformerless inverters breaking both the positive and negative, but it appears just breaking the positive that it works just fine with my pair of Classic 250's. I'd have purchased this unit months earlier if not for that confusion. Just my thoughts. Love your products.