I bought this along with a Blue Sea Systems 30 amp AC circuit breaker. (If you buy a switchboard, make sure you get one with the new ELCI circuitry you need.) It fits perfectly, is easy to put on the first time, and works great. The panel comes with two 15A circuit breakers which I used. for battery charging circuit and sockets on the starboard side. I bought this circuit breaker to turn on a powerful heater or microwave oven in cold weather. protected by 20A GFCI, all rated WR (Water Resistant). Boat cable 12/3 is suitable for 20 amp AC circuit. As with anything electrical, make sure you know what you're doing! As a friend recently said, if you make a mistake plumbing, someone will get wet. If you make a mistake with electricity, someone will die.