Blue Sea 4 position 300 amp m-Series Mini Selector Battery Switch - The battery switch switches isolated battery banks to all loads or combines battery banks to all loads. It features a &';make before break&'; contact design which allows switching between battery banks without power interruption Switches isolated battery banks to all loads or combines battery banks to all loads Make before break contact design allows switching between battery banks without power interruption Isolating cover with snap-on sections protects rear contacts Case design allows surface, front panel, or rear panel mounting Ignition protected-safe for installation aboard gasoline powered boats