The Heat Pants 2.0 are extremely flexible thanks to the highly elastic 3D stretch fabric & guarantee a comfortable fit. The extra-thin design means that they fit under any trousers. The soft inner plush ensures a comfortable fit & a balanced heat development. The heating element is integrated into the front thigh area & the batteries are attached directly to the waistb&. The lithium packs are attached above the waistband &, depending on the battery type, provide up to 11 hours of heat. Features Insulated heating zone in the thigh Soft inner plush for extra insulation Highly elastic 3D stretch fabric for a perfect fit Extra elastic & soft, less bulk Can be worn under any trousers