This is a clone of a Yamaha ET800 design... A generator made in the 1970s. It has little to no voltage regulation other than the fact the governor tries to spin it at 3600 RPMs (3000 RPMs if in Europe.) Add or drop a load, and you will get a spike.
For a C-note, it is an OK generator. Make sure to pull the spark plug and replace it with a top brand, follow the oil/fuel mixing directions exactly, and break it in as per directions. However it is cheaply made and puts out extremely dirty power.
Personally, other than price and the fact they are "disposable", I wouldn't get one. I'd save up a few more C-notes and buy a Champion open frame model which will last a lot longer.