The surge protector itself appears to be well built and will probably work well should a surge occur, although there's no real way to tell. But I have a problem with the installation instructions provided, and in fact almost every video or guide you can see on the internet for adding surge protection to an AC cutoff. They will almost always tell you to connect the surge protection wires to the same spade terminal as the AC line is connected to - please don't do this unless your circuit breaker or disconnect switch specifically supports more than one wire under the spade terminal! This is not a secure connection and can be potentially dangerous. Connect a nut or Wago wire to the AC mains and surge protector, and connect the isolator so that only one wire is under the terminal lugs.