It's a Variac, works fine for what it is. The wiper contact might need a few operations back and forth to clean the contact surface, but it's fine in general. It's about 1/4 the price of better made USA products, but this gets the job done for the price even though it's not top quality.
Everybody complaining about the dial - the dial is calibrated in PERCENT, not voltage. So if the dial is set at 100, that is 100% of your incoming line voltage. If your incoming line voltage is 120VAC, then the output will be 120VAC, and so on. If your incoming line voltage is 125VAC, and the dial is set to 80%, then the output will be about (125 X 0.80) = 100VAC. Actually the adjusting dial is reasonably close. The AC voltmeter is a sort of a joke but at least it gives you an idea.
For everyone complaining that the this Variac (Variable Transformer) is not isolated from mains - of course it isn't. By definition a Variac is NOT isolated. If you want an isolated variac you plug this unit into an isolation transformer upstream - or you can plug in an isolation transformer downstream from this unit, and then plug your device into the isolation transformer.