I am aware that voltage converters are not transformers, but a converter serves well enough for average traveller's gear. Transformers are too large and heavy to be practical to pack.

The best kind of converter has two settings.

One setting allows high enough wattage to handle today's 1875 watt hair dryers and other heating-up appliances; the other setting is 50 watts for the small stuff.

Also needed is a foreign plug adapter with the correct prongs for the electric
outlets. Even if your voltage converter has the right prongs, in Europe the outlets are recessed so the converter prongs will not reach and you still need the adapter.

When you go to plug your US plug into the foreign adapter, it only has two slots. If you have US three prong plugs, you need a US grounding adapter that takes your three prong plug down to two prongs. This is the same kind of grounding adapter used in older homes to enable three prong
plugs to be inserted into old fashioned two prong outlets, easy to find in any hardware store.