Abstract: An envelope for keeping susceptible materials such as drugs within an acceptable temperature for durations to allow for transport of the drugs to recipients the cold keeping envelope having an outer insulating envelope and an inner envelope or envelope like shape having liquid or liquid like material to be frozen held within a plurality of separate cells forming the inner envelope such that when the liquid or liquid like material is frozen solid, the inner envelope or envelope like shape can still be easily opened caused to open by relative rotation of separate cell to allow for insertion of articles therein. There are further described constructions including an outer envelope of bubble pack with a metallised reflective surface, joining of inner and outer envelope parts, double thicknesses of bubble pack material, use of frozen cells on one side only of the envelope shape, and shapes and relative location of cells to facilitate bending of the frozen materials.