The MRE meal seem to weigh more (wouldn't want to hump 9 of those meals stuffed into my ruck
pack) than the C-rations and required a bit more expertise than the C-rations to prepare.
With the C-rations all you needed was a P-38 and a piece of C4.

Anyway, the meal included the main course, "Beef Ravioli" along
with a fudge brownie, apple slices/sauce, crackers, cheese spread, hot
chocolate and a pouch with Tabasco sauce, gum, toilet paper, matches and
spoon (no cigarettes). The meal was heated by adding just a bit of water
and waiting 15 minutes while the enclosed heating source (a chemical
reaction type feature not C4 as we used) heated the meal. Once heated
you opened the pouch and consumed the meal. Being an FNG I didn't get it
quite hot enough on the first try so I popped it into the microwave
(just like they would do in the field). I must say the meal was pretty
tasty but the portion seemed small, couldn't hump all day, dig in at
night and be nourished by that portion.