G'day Tracey,

The next size tri-fold is almost double this size, so you shouldn't have any issues with this size fitting.

We've previously had a question around how many to use in an esky/how long they'll stay cold for, and unfortunately, it's like asking 'how long is a piece of string'.  There are too many variables to give you a definite answer.

In the specifications, we state that Thermal Ice has recommended 1 Sheet per 18-24 Quarts or 17-22L.  Based on the size of your Icebox you'd need 2 of these large icepacks.  I would personally use 3 if you can fit them in with your food, just to cover you in the hotter weather of summer, and as a fail-safe if you'll need to be opening your Icebox more often.

Hope that helps.

G'day Kristyn,

Its impossible to tell you how long these will last, sorry.  There are so many variables such as ambient temp, type of eski used, how often it's being opened, how much stuff is in the eski, if the stuff in the eski has been pre-chilled, etc.
The only thing we can say is that these will stay cooler 3 times longer than ice.  The product review space would be a great area to get feedback on real-life use cases.  A lot of people have no trouble with these for several days.