ive used a cheap silver flask for the last 5 years to keep my bait frozen when out.i noticed last winter when taking bait out to put back in the freezer it was starting to defrost.i was only out 3 hours today and took some frozen crab in the flask and when back home I went to put it back in the freezer and it had defrosted fully.anyone recommend a good flask.maybe mine is just past its best as it used to be ok