I personally tape a heat pack to the bottom of the cooler , cover it with newspaper after packing frags I put more newspaper then place the styro lid with another heat pack taped to the inside of the lid.That way the frags stay nice and cozy and usually make it without any problems. One needs to remember that temps are starting to dip below freezing at night ,and not much above durning the day, in most of the northern states Also the 12 Hr packs IMO arent good enough they "die" before the package is delivered. Go for 35-40 HR. packs. A little security goes a long way if your package gets stuck in limbo for an extra day.