I agree with the ACR, great product. The switch isn't a great idea though. It is inflexible, not allowing either bank to be used for starting or house loads. The only way to start if the aux/start battery is dead is to combine the house bank with the dead battery - never a good idea, especially with banks of unequal size. The switch is really designed for small boats with equal size banks - like a 20' fishing boat with a single battery in each bank.
The 1/2/both switch is a lot more flexible as it allows you to use either bank for starting. The ideal is 3 simple on/off switches, one for start, one for house and one to cross loads without leaving a dead battery in the circuit. Below is the Blue Seas version wiring diagram, but easy to create with 3 switches (Blue Seas 6006 or similar).