Add to any existing Platypus hydration system to fend-off freeze-up in cold weather or to keep drinks cool in summer.
In summer you take a drink and the water that's actually in the tube has heated up and is warm, just as you suck past that and get to the still cold stuff in your bladder you've had enough! The insulator keeps the tube bit cold as well.
More important in the winter though, when water held in the tube could freeze - the insulator becomes even more important. The bite valve cover keeps the bite valve clean.