Engel Heavy Duty Malibu Soft CoolerWhat separates the Heavy Duty Soft Sided Cooler apart is that it's entirely welded, while most others are sewn. By welding all seams, warm air is kept out, dramatically increasing the life of the ice inside. The welded seams ensure there will be no air or water leaks it to keep beverages cold for up to 3 days. The front and back sides are laminated with a Thermal Plastic Urethane (TPU) film, adding another layer of strength and puncture resistance.