Brand new, unused L size x 2 [Semi-permanent reusable] Our cool neck ring uses the latest "PCM material" and freezes when the temperature drops below 28 degrees Celsius. When the temperature exceeds 28 degrees Celsius, it absorbs heat and slowly melts while providing a cooling sensation. Once melted, it can be cooled in cold water or a refrigerator, freezing in a short time, making it eco-friendly and semi-permanently usable. [Great for cooling in various summer situations] It's perfect for camping, walking, jogging, mountain climbing, fishing, indoors, fireworks displays, watching sports, offices, and many other situations.