Mm...just to add: we all bring multiple digital devices, some on USB, others like laptops, cameras or drones require a separate DC power supply. Two, many hotel rooms only have one available AC outlet(110 or 220 and with different plugs). Three, available AC outlet is inconveniently located and requires an extension cord. Four, multiply those devices with the number of people in your party. Big problem. My solution that satisfactorily solves all 4 problems is this all-in-one: https://www.amazon.com/PRITEK-Portable-Protector-International-Extension/dp/B075164753/ref=sr_1_3?crid=PXZWJLCQ55TO&keywords=pritek&qid=1550894817&s=gateway&sprefix=Pritek,aps,330&sr=8-3 Tested this. Note that although this device is autovolt, it is not a transformer (step-up or step-down).