Firstgear Heated Pants Liner - Small/Black Available in 90-watt and 65-watt versions. Designed to be plugged into a DC power source or battery pack. Heat-trollers provide you with multiple ways to control the heat output in your heated gear. Exclusive dual-zone heating system allows you to use the single or the dual Heat-troller without rewiring the liner. The liner is rated at 110 watts at 12.8 volts