Kryopacks or icepacks, what ever you want to call them… They are the flat, flask shaped things you put in your freezer that become solid blocks of frozen “stuff”. You can then drop them in a cooler. They are great for keeping anything in a cooler, cold, for about 36hrs. Tidy, don’t have to deal with ice or melted ice in a cooler. I bought mine at a dollar store. They came in 2 sizes, 16oz and 8oz. This was about 30 months ago, sorry, I lost the receipt from the dollar store. I can only give approximate times, but my estimate is close. Within the last 2 weeks cracks began to appear in the 16oz ice packs, in 9 of the 10 I purchased. It’s amazing they all began to fail at once. One began leaking “blue stuff”. No cracks or leaks have yet appeared in the 8oz size. I have no doubt they will start to crack soon. These things are very handy. When I grocery shop in the big town, anything frozen I buy, will begin to thaw on the edges by the time I get home. I always take a cooler to the big town with a few ice packs in it. Any who… they last about 30 months when used constantly… for planning purposes.