In the United States, medium-voltage (MV) power distribution typically uses withdrawable circuit breaker switchgear (WCBS). Withdrawable breakers allow for regular maintenance and provide an easily visible confirmation of circuit isolation but at a cost — having removable parts and the act of inserting and withdrawing breakers could result in the possibility of arc flash incidents. Modern fixed circuit breaker switchgear (FCBS), which uses highly reliable and virtually maintenance-free vacuum and gas breakers.