Product Description Siemens main breaker kits are used to convert the Ultimate type of main lug load centers to main breaker load centers, or can be used as a replacement main breaker in main breaker type Ultimate load centers. Ultimate load centers are the current load center in production and went into production in 2002. Check the load center wiring diagram for confirmation. Siemens strongly recommends against the use of "used" breakers. The installation of used breakers in a Siemens panel will void the warranty on the panel. Siemens does not sell used breakers and has not approved any 3rd party sellers to do so. From the Manufacturer SIEMENS main breaker kits are used to convert the Ultimate type of main lug load centers to main breaker load centers, or can be used as a replacement main breaker in main breaker type Ultimate load centers. Ultimate load centers are the current load center in production and went into production in 2002. Check the load center wiring diagram for confirmation.