It looks like what they are offering are the old versions of the air force ration. The new ones are Survival, General Purpose, Improved. GPI. The one in the picture is what they used to make before they "improved" it. (I don't know what they improved, but, they have been making the new version for several years, so I would check the dates on any older ones.)

The key thing for the survival rations is they are designed to not induce thirst, because they assume you might not have access to much water in a SERE situation. They are mostly carbo's, only a little protein. They are the rations in the ejection seats I believe. They were supposed to keep you alive for a couple days until the Jolly Green arrived.