The best cooler I ever saw was home made. It was made of wood, and a few inches of Insulation Sheathing. Granted it was as big as a freezer, but it kept things cold longer. Surprised me when I pulled a beer out of it. Two weeks after a wedding, and it was still cold. Not 40 degrees cold, but about 50-60 degrees. That was after sitting out in the July sun. If I ever have the need for a cooler again. I would make one the size I needed.