The Square D QO 100 Amp 20-Space 20-Circuit Convertible Main Breaker Outdoor Load Center is UL listed for residential, commercial and industrial power distribution. This load center is built with a shielded, copper bus bar that is plated for reliability. QO load centers are tested and listed only for QO circuit breakers. QO load centers are the "World's Finest" designed with industry leading features for flexible application. QO load centers include features engineered for fast installation and wire savings.