Very efficient insulation. None of the light weight coolboxes available here performs like this one, only to the heavy commercial boxes come closer to these extremely light weight ice boxes. Their claim of 5 days is believable if you pack the box full same temperature items and ice pack.
Great Coleman quality. I used a Coleman for 20 years, but now had to change as the old one was getting too tatty to use in public, though it functioned very well indeed. This one is large and keeps drinks really cold until the next morning after the party - so we can finish the leftovers for lunch!