Code-gauge steel enclosure. Single phase, 3-wire, solid neutral, 4 spaces and 8 circuits maximum 1-pole, 2 QP breakers maximum 2-pole, 120/240 V. 10,000 AIR. One piece plated aluminum bus bar. 100% circuit breaker twist outs. Positive load side circuit breaker hook rail. Suitable for use as service equipment when a main breaker (100 A maximum) is back-fed in a branch position and used with main breaker retainer clip No MBR1. When used as service equipment, any unused neutral position may be used for equipment grounding. Rotate entire device 180 deg for bottom feed. Gray enamel finish. 6-5/8 in x 12-5/8 in x 3-1/2 in. UL listed, complies fully with NEC and UL requirements for Class CTL.