Vietnam uses Types A, E, or F plugs with two flat pins, two round pins, or three round pins, respectively. The usual voltage is between 220V and 240V, 50 Hertz; but sometimes you encounter 110V, also at 50 Hertz, just to confuse things. Two-pin (ungrounded) plug is more popular than three-pin one. If you have any devices needing a special outlet, please bring its adapter kit. The best investment is a universal AC adapter, which will enable you to plug it in anywhere without frying the innards.