Fieldsheer Women's Premium 2.0 Merino Heated Casual Socks - Whether you're in deep backcountry powder or an early morning job site, keep your feet warm and improve circulation to avoid stiffness, muscle fatigue, and soreness. 3.7v Lithium-Ion battery that provides long-lasting warmth for up to 10 hours on a single charge Bluetooth control powered by MW Connect technology with 4 heat settings Odorsheer and sweatsheer technology Merino wool blend Style: MWWS07010221