Welded sheet steel. Single phase, 3-wire, split neutral, 12 spaces/12 circuit, 120/240 V. 22,000 AIR factory installed main breaker. Comes with a ground bar and a combination cover for added protection. Shielded copper bus bar. 2-1/2 in knockouts located on the top and bottom. Accepts QO circuit breakers and is compatible with overhead and underground service feeds. UL listed.