The butter tins are quite a bit larger than you might think.  This doesn't help though since the waterproofing is achieved by a large rubber / plastic insert which takes up a bunch of room.  Further they are truely bomb-proof!  They are made of very thick aluminum.  I can't imagine actually carrying one in a pocket due to the wieght and the size but There may be reasons to use them.  I can't imagine one now but If anyone does let me know.  I don't need butter on my hiking badly enough to stick one of these in my pack full of butter - that much is certain.