FirstGear's Heated Jacket Liners warm you in seconds and are designed to feel as if they're not even there. High tech, moisture wicking fabric with stretch side and back panels, keeps the garment tight against your body for optimal heat transfer, while reducing bulk. Seven heat panels cover the chest, abdomen, arms, collar and entire back, delivering more heat than any other garment. Soft and flexible carbon panels, shaped for maximum heat transfer. All this efficiency means less insulation and power is required to deliver and retain the desired heat.