These hand warmers feature a temperature sensor chip offering 3 heat levels up to 130 ℉. They have a 6000mAh battery providing 8.5-20 hours of warmth, with indicator lights for battery and heat status. The design is ergonomic and slip-resistant, with UL, CE, and FCC safety certifications. The price drops from $29.99 to $19.99. Shipping is free for prime members or on orders over $35.