Best to try and search for this and have a good read.
I added a 50a hard wired version on my new fiver. Its helped alert me to problem wiring twice in the last month. Basically it protects your camper power and electric systems from; low and high voltage, surges, mis wired pedestals, etc. many have plugged a 30a trailer into a 240v welder outlet and fried many expensive electric components.
Personally, I won't go without. But, it was hard to spend the $$ when its not a cool hands on device
Joel and Teresa
2016 Sabre 34TBOK
2006 GMC 3500 CC LB DRW 4X4