These can only be used in the US to operate UK electrical equipment if you are relocating or living there. The 1500V version was able to run a TV, DVD and surround system. I have 2x 1500V (price £100) and 1x 500V (price £60), which is half price on buying new.
From the Airlink website:
Use UK electronic equipment in America
230V output to run British appliances in America
120v Input fitted with American 3pin plug
Conforms BSEN61558-2-13 CE & RoHS
All transformers from 1kVA and above, are fitted with surge limiters
British Built