Most modern smartphones, tablets and laptops are dual voltage. Smartphones and tablets can generally be charged with just the USB cord and international plug adapter, but you will of course need your laptop's full cord with adapter brick. We checked with Apple to confirm that both the iPhone itself and the charging bricklet are dual voltage--but if you want to be extra careful, you can eschew the USB ports on travel plug adapters, and use the power bricklet in the normal plug outlet portion of your adapter instead. Many travel size hairdryers, curling irons and flat irons are dual voltage, as are the chargers for high end electric toothbrushes. However, in our experience, many of these toothbrushes hold a charge for upwards of a week, so you should consider leaving your charger at home if you're traveling for 10 days or less. If you're unsure, check the labeling, original packaging, or contact the manufacturer. You can always choose to play it safe by bringing along a voltage converter in addition to plug adapter.