Take advantage of the REDARC 30A Circuit Breaker Kit for your three-axle electric trailer brake controller setup. With the bulk of work done for you the battery connection wire has a robust protective conduit, heat shrink, and crimp already attached. Plus, the brake controller connection is pre-crimped with heat shrink. Both wires just need to be affixed to the circuit breaker with the nuts provided in the kit along with a detailed wiring diagram.
Included for your safety is a protective boot to cover the circuit breaker and protect against any accidental terminal shortage.