【Hot GEL RING】 A convenient gel ring that gently warms your neck! The M size starts to generate heat and harden when you gently bend the metal inside. The maximum temperature is about 52°C, and the warmth lasts for about 1 hour. ◎ Reusable and economical! ◎ Size details: • Inner diameter: 13cm (Thickness) Approximately 2.2cm (Inner circumference): Approximately 44cm (Neck size guide): 42-46cm Recommended for outings on cold days and for desk work♪