I thought about putting a hardwired surge protector in our 25FB which would have required removal of the queen bed and the plywood sheet under it to place the unit as close as possible to the service entrance.
A surge protector is like the sacrificial anode on a boat in that it goes or dies rather than the electronics or motor. I elected to go with both the 30 amp (for the generator or older trailer parks as I had it for the 25FB with 30 amp service) and 50 amp portable units so if they do their job, I do not have to tear the trailer apart to replace them.
The links below are just information links for these two models which are available at Camping World and other RV equipment stores.
Portable 30 Amp RV Surge Guard by TRC - 34730
50 Amp Portable RV Surge Guard - 34750
If one wants voltage regulation as well, then there is a transformer and capacitors inside a heavy box to regulate the voltage within certain parameters. Too low voltage can burn up compressor motors on air conditioning units. Here are information links for voltage regulators and I have seen them at Camping World:
Surge Guard 30 Amp Voltage Regulator
Surge Guard 50 Amp Voltage Regulator
The common thread is that the 50 amp rated equipment is priced much higher than the higher capacity parts actually cost for more profit.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels