Burton insulated the Vent Mitts with Thermacore™ but must have realized that, while this kept your little grom's hands as warm as possible, there was a chance that their little hands would overheat under the temperature. To combat this, Burton added a vent pocket, so if their hands are too warm, kids can vent off some excess heat. But, because Burton's designers are smart, they didn't stop at a vent, creating a full fledged pocket so that when the weather really gets cold, a hand warmer can be dropped in the glove itself. All this, plus the DRYRIDE 2L Ultrashell (which keeps moisture where it belongs, outside) mean that the Burton Vent Mittens will always keep any kid's hands dry and at the perfect temperature, no matter what the weather decides to do.