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 also included in MRE.
They are small grey 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 in Halo: Contact Harvest by Private Wallace A. Jenkins.
