What separates the Engel Heavy-Duty Soft Sided Cooler from the competition is the fact that the Engel HD20 is entirely welded while most of its counterparts are sewn. By welding all seams, warm air is kept out, dramatically increasing the life of the ice or ice packs inside. The welded seams ensure there will be no air or water leaks, and allow the soft-sided HD20 to keep beverages cold for 3.5 days, according to an independent review. The HD20 boasts an outer shell composed of durable 840 denier fibers, which provide maximum strength and abrasion resistance. The front and back sides are laminated with a Thermal Plastic Urethane (TPU) film, adding another layer of strength and puncture resistance. The cooler has closed-cell foam insulation, preventing air from passing through it and improving the thermal range of the cooler. With a welded waterproof and air resistant zipper that requires lubrication for optimum function, this cooler has a capacity of 22Qts and can be carried with tote handles or with a single padded strap. Like other Engel models, the cooler has an integrated bottle opener. New in this cooler is patent-pending vacuum valve technology. Customers should use a vacuum to suck out excess air before the first use for optimum performance