A lunch cooler bags uses thick thermal insulation around its body. The insulation of a picnic cooler allows you to carry an assortment of fresh food and drinks while keeping them safely chilled for longer periods. This function works by reducing the process of heat transfer. Essentially, insulated materials prevent heat from entering or leaving the container; thus, cold items are kept cold because the cooler prevents the transfer of heat into the container.

This is usually foamed in place and is typically of urethane composition. Newer designs may also utilize blow-molded plastic, polystyrene, polyethylene, polypropylene, ABS resin, or any other suitable type of insulation material. Lunch cooler bag come in different styles and sizes---depending on the specific needs of each user. There is a wide array of designs available for picnickers, backpackers, mountaineers, travelers, students and employees who bring their own food to work. There are also those made with insulated fabrics and those that are thermoelectric units--they are heavier but can cool your food in pack form. The designs also provide convenient waterproof lining to further help avoid moisture from coming out from inside.

Given its features, a picnic cooler is a perfect alternative to the traditional picnic basket or lunch bag.