The Hotronic BD Anatomic Insoles are pre-installed with Hotronic Heating Elements for superior heating coverage and fit. Customize your fit further by trimming around the toe to perfectly fit your liner and heat-mold to your specific foot shape. Don't let cold feet ruin your day on the hill! Grab a pair of Hotronic BD Anatomic Insoles, a battery pack of your choice, and get out there!