Unlike many others, the seams on the rugged tear- and water-resistant coolers are welded closed, not sewn. This keeps warm air out and cold air in, and it means no air or water leaks. This also helps drinks stay cool for up to four days (yes, days), along with an assist from a layer of closed-cell foam insulation. The perfect finishing touch? A built-in bottle opener, of course, that makes one of these durable coolers an all-in-one cold refreshment station.