Warmthru Rechargeable Heated Socks- STANDARD - WarmToTheBone - Bike, Ski, Walk Modular design so you can replace all the bits separately. 100% Washable - because heat-element is easily removed from fabric. Rechargeable Lithium Ion batteries - price includes two 3.7V Li-ion batteries with on-off switches. 2 3.7V Li-ion Batteries last 3 to 3.5 hours used continuously. Warmthru Heated Socks good for Raynauds