The 3.7V Premium Bluetooth heated sock battery is part of the line of Micro USB charging Mobile Warming batteries. Mobile Warming uses only the highest quality Lithium-ion batteries to ensure long-lasting power and battery life. Their batteries are designed to power your Mobile Warming product for hours, ensuring you stay warm and comfortable. The 3.7V Premium Bluetooth battery is exclusive to their Premium BT heated sock and can be controlled with the MW Connect app.