What is the difference between a QO and QOB breaker?
QO and QOB
Electrical Distribution Systems
A QO breaker is plug on mounting, and can be used in QO load centers, old NQO and NQOD panelboards, and current NQ panelboards. A QOB breaker uses a bolt-on connection to the bus, and can be used in old NQOB and NQOD panelboards, and current NQ panelboards. Otherwise the breakers are the same.