I meant to say, with the electronic ones some are pre-set to the country they are purchased ie: 0.8mg for the UK so you get a green light if under and red light if over, however this reading will be incorrect if in France and many other parts of Europe where I think their limit is 0.5mg ( Norway, Poland, Sweden it is just 0.2mg ) So if taking abroad make sure it is one with a digital readout rather than just red/green lights.