HEAT FACTORY PRO FLEX OUTDOORS INSOLES SMALL ProFlex Heated Insoles are great for keeping the cold at bay this winter. They keep the feet warm, without getting too hot. Made from polyurethane insole material, the insole will allow you to stay comfortable in your shoes all day. Heated insoles offer convenient remote operation-no worries or external batteries- and at least 2500 hours of use. Using the Pro-Flex insoles is simple, just adjust to the needed temperature, choice of no heat (standby), medium (100F) or high (111F).