/diy/ - Do It Yourself

>>1266926
They are already filled with insulation. Usually, some form of polystyrene but older ones were sometimes filled with fiberglass and an air gap on the interior side. We're talking old as balls here though. Like all metal Skotch Koolers from the 50s and shit. Once coolers standard to have a bunch of plastic in them the rigid insulation became the norm. Really though, unless you are getting a Yeti or something like that they all have about the same cooling performance. The only thing really different is things like build quality and materials. In cheaper models the seals won't be as tight, the plastic not as thick (less durable), the hinges will probably break, and it is almost certain to oxidize and turn brownish after a while.