Thermic ic 950 Smart Pack Suitable for use with all ThermicSoles and boots with ThermicInside Ultralight lithium-ion batteries providing warmth for up to 18 hours: 1: 37C / 99F 13 - 18h 2: 45C / 113F 6 - 8h 3: 70C / 158F 2.5 - 3.5h The 3 heat levels can be set at the push of a button: 1: 37C / 99F 2: 45C / 113F 3: 70C / 158F The Impulse Control stimulates the blood circulation Standard charger (EU/US/UK) with automatic charging function, Extremely short charging time (2-3h)