This 50 amp DC circuit breaker features a cycling automatic reset. They are sometimes called short stop breakers and are used in many applications, but in a properly wired 12v system, one should be installed on the line running between the positive terminal of your battery and your DC fuse box, within 18" of your battery. You will probably be using one with your breakaway switch too.
The copper terminal connects to the wire coming from the battery. The zinc terminal connects to the line running from your 12v fuse box and converter.
This is a plastic unit which is preferred in a travel trailer because it resists vibration better.
It includes a red safety cover to prevent accidental shorts and to keep the breaker clean and dry. Please always use the cover.