This is an Accufiber Guard necklace. The size is 51cm. I tried it on, but it doesn't fit, so I'm selling it. The following is a product description: This product contains the miraculous hot spring microorganism "Onsen Algae RG92," which is supported by many athletes. "Onsen Algae RG92" is a new algae (patent) discovered by the SARABiO Hot Spring Microorganism Research Institute in Beppu Onsen, Oita Prefecture. It has been revealed that this new algae "Onsen Algae RG92" is one of the main reasons why "the body feels better when entering a hot spring." "Onsen Algae RG92" has been found to provide various effects, such as relieving accumulated body fatigue, stubborn skin problems, anti-inflammatory action, anti-glycation action, antioxidant action, and improved immunity.