This is just the right size to get 4 in the bottom of a igloo 34 litre cooler box. The large size means they have greater thermal capacity and they will last a long time.
Leave them overnight in the freezer horizontally and I use them the next day going fishing. If you don't lay them carefully in the fridge they may come out a bit pregnant. Buying in bulk, I bought 8, spreads the one off delivery cost, which keeps the price low.