Stash Tube MkII
A simple no nonsense push top tube with a reliable seal. Approx 3" long they can be hidden almost anywhere and if the need arose you could 'deep carry' it to retrieve it later. Alternatively, could also be 'stashed' externally easily, in a variety of other locations.
A perfect addition for storing a survival kit for example, possibly one of the few things that has a hundred uses and the more you use it, the more you will find.