PTX Backpack Cooler Black w/ Silver. The PTX Backpack Cooler is so versatile and handy, you will wonder how you have managed to live your active lifestyle without it! With a fully-insulated interior liner that's also water-resistant, you can use it as a food and beverage tote or as an all-around activity tote. With a variety of expandable pockets and front-mounted stretch cord, the PTX Backpack Cooler can accommodate and store items