High-Purity Terahertz Massage Tool Can be used on the entire body. Terahertz effects include: Improved immunity Cell activation Improved blood circulation, relief from coldness Fatigue recovery Warming the body from the core, and more. It is said to be effective to roll it around and loosen up the area. The size is shown in the photos ^ ^ There are multiple available, so please comment if you are interested. Natural stone Terahertz ore Power stone Stamp type