Thermic rc 1600 Smart Pack Suitable for all SmartPacks (rc 1200 / ic 1200 / ic 950) Ultralight lithium-ion batteries providing warmth for up to 29 hours: 1: 37C / 99F 21 - 29h 2: 45C / 113F 9 - 13h 3: 70C / 158F 4 - 6h Simply replace existing 1200 / 950 battery with Upgrade 1600 battery Rechargeable with SmartPack global charger and standard charger Extremely short charging time