This is a terahertz necklace (*ˊᵕˋ*) It has an adjuster, so it's 40cm to 45cm. Terahertz is an artificial mineral made from high-purity silicon. It has a frequency of 1 trillion vibrations per second, "terahertz waves." It has a longer wavelength than far infrared rays and acts on the cells in the body, promoting blood flow, increasing basal body temperature, activating cells, boosting metabolism, and providing benefits such as improved sleep and beauty effects, etc. (*ˊᵕˋ*) #terahertz #healthnecklace #sleepeffect #beautyeffect