Rations
From Halopedia, the Halo wiki
Template:SeeWikipedia Rations, like Meals Ready to Eat, are food for UNSC personnel to eat in dire situations, such as being in a crashed Pelican or surviving through enemy patrols.
They are small, gray, cylindrical tins containing set ration meals. There are five of them in the armoury on Cairo Station, about ten on Outskirts, and six in the Brute armoury in Uprising.
They are mentioned in Halo: The Flood, when Master Chief selects components from two MRE's, and also in Halo: Contact Harvest, by Private Wallace A. Jenkins.
