Prepaid currency card

I’m not sure whether it is due to doing some work on pre-paid cards, but the Caxtonfx card seems like a very good idea for purchases abroad. Summary: you load money on the card and spend it abroad, without the FX fees you would normally attract. they also look to have about 1%-10% better exchange rates than other options. Seems like there must be a catch, but I can’t see it.