Square D QO 1 frame-size 100-Amp Double-Pole Main Breaker. Used for overload and short-circuit protection of your electrical system, this breaker is compatible with QO and Homeline load centers, CSED devices, and NQO panel boards rated for 100- to 125-Amps. It accepts aluminum or copper #12 - 2/0 AWG feeder wire. To ensure safety, it is both UL listed and ANSI certified. The ANSI-certified and UL-listed unit is rated for 120/240 VAC and 22,000 AIR. QO circuit breakers have features no other manufacturer can offer. They come in many different sizes and can meet the needs of virtually every function in your home or business. These types of quality, industry-exclusive products keep the Square D brand ahead of the competition and are builders' and electrical contractors' first choice in electrical protection.