The 3.7v Powersheer Wireless Heated Sock Batteries are premium power banks for your Mobile Warming Wireless Heated Socks designed to provide longer heat times between charges with its 4000mAh capacity, and they feature USB C quick charge input for faster recharge times. They can be used on our Premium 2.0 Merino Socks to increase heat times between charges, control of the socks will be via the wireless remote control not Bluetooth. Whether you’re hitting the slopes, trekking through the snow-covered landscapes, or simply bracing the winter chill. Embrace the winter season with the assurance that your feet will stay warmer longer, thanks to the advanced features of these exceptional batteries. Specifications: Rating: 3.7volts, 4000mAh Input: USB C 5V@ .9A Charge Time: 5-6 hours Size Inches: 3.562in x 2.5in x 0.5in Size Metric: 90.5mm x 63.5mm x 13mm Garments Compatible: Mobile Warming Wireless Heated Socks sold at Costco