Unfortunately, in the UK Prague Powder tends to be made wth nitrite rather than nitrate (particularly the Cure Number One variety), being designed for the industrial sausage-maker, and thus you need to be extremely careful when measuring quantities for your home cures - in the order of tenths of a gramme. Get it wrong and you will not be a very well bunny.
Best to stick with the old fashioned saltpetre, which is cheaper and less of a bother to use.