Yamasin Seikyo Ice G3.0R Black with Safety Cord M ICG3R-BKC-L This product uses a special material that changes from liquid to solid when cooled, solidifying even in temperatures below 22°C or in water. When the outside temperature is 25-35°C, it can be cooled for approximately 2 hours to 1.5 hours (approximately 4 hours to 3.5 hours for the 3.0 version). It can be used repeatedly, making it economical.