I've used ziplock bags too, when I was on Dartmoor with Leon & Neil this summer. Mine measures aprx. 20x25cm ... bit smallish - so I suggest going for anything about A4 paper size if you can find them in the supermarkets.
A smaller one works, but there's a chance you tear the plastic, or not everything fits in it. I repacked this package in a transparent bin liner and twisted the top and taped it to the back. Think it was a bit of an overkill, but it kept the lot dry - which was my aim.
Ration / contents / idea etc. borrowed from British Red
(Thread must be here somewhere)
My ration: (packed in ziplock bag ... which is poorly visible ...
)
Front:
Back:
Contents:
Looks not much, but I'm not a very big eater - and I have a separate bag with a brew kit (hot chocolate, with loads of sugar - I still got all my teeth Leon
) and sweets, etc.
The big package in the bottom pic is sufficient for 2 persons, or 1 for 2 days, or 1 for lunch and dinner (if like eating stuff twice on the same day)