Worth mentioning that they are absolutely not safe as the exposed prongs are energised. They are called suicide cords for a reason. All it takes is to plug the cord into a running generator or working outlet first and the exposed terminals are now live.

Its also worth noting that they very often kill linesmen working to desire the utility because people use them to hook up their generators without turning off their main breaker which back feeds onto the grid.

Proper generator inlets are very readily available and if you don't want to go that route, just plug your fridge and other important devices into your generator with extension cords.

Murphy's law says it will be used wrong, and as such it is a bad design and a bad idea.

There are alternatives that are better, this has only the advantage of being cheap.