Capacity: If you’re only planning to use your cool box for fridge overflow in the kitchen, cellar or garden, you can afford to invest in a 50-litre-plus whopper. But bear in mind that cool boxes, like fridges, work best when they’re full. A 47-litre cool box is big enough for well over 80 regular cans of drink. You'll want to make sure that you keep the windows open if you're driving with dry ice. As it heats up it turns into a gas and if you don't have your windows open it can remove the oxygen from your car and make you pass out or even worse kill you. This means that even if it’s 90 degrees outside, your ice cream will still be nice and cold when you reach your destination.

While it might seem counterintuitive, leaving melted ice water in the cooler can help maintain a colder temperature. It acts as an additional thermal mass, helping to keep the contents cold.

Capacity: Coolers are available in a range of sizes, from a five-quart cooler to carry your lunch to a 125-quart cooler that's large enough to hold more than 200 cans. Because a large-capacity cooler can get quite heavy, consider buying one on wheels — or even two smaller coolers (one for drinks and one for food) for easier transport.

Waterproof capabilities: particularly important for cooler bags if you're taking them out and about, but also that the lining is leakproof The better you can do this the longer your food will stay frozen in your cooler. How Long Will Different Foods Stay Frozen?To keep food frozen at the ideal temperature you want these items to be around 0ºF (-18ºC), which is the internal temperature of your freezer at home. If you often find yourself traveling with frozen foods, we highly recommend investing in a good quality travel bag. It will make all the difference in keeping your food cold and intact during transit. Southwest Airlines Frozen Food Policy