Graham we use an ICEY TEKI 25lt it will fit 3 x 1lt bottles across the bottom, we freeze one overnight in the camp Kitchen the previous one will be 1/2 melted and the third will be good and cold so we start using it and just keep grabbing a fresh one each day and into the freezer over night, done 25,000k of touring that way, Tassie, Darwin, Red Centre. would do it any other way Light high tech construction and strong.