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 a relaxing sleep effect, beauty benefits, etc... are expected (*ˊᵕˋ*) #terahertz #healthnecklace #cellactivation #sleepeffect #beautybenefits