I bought one of these from Amazon last year and I've received two warning emails from Amazon, along with a refund. My use case is connecting a portable generat

I bought one of these from Amazon last year and I've received two warning emails from Amazon, along with a refund. My use case is connecting a portable generator to my house. It's all completely safe if you know what you are doing. You turn off the main breaker (between the meter and the AC mains connection), then you plug one end of the "suicide cable" into some outlet, and the other end into the generator output. Another related use case is to connect the two different phases together so the generator can power the whole house instead of half the house. For that you need two of these.