The main feature of the device 17 layers system is the thick Amethyst layer releasing FIR rays and negative ions. Mini mat 31”x20” contains 8.5 pounds of 100% natural untreated the most expensive A+ grade Korean tumbled Amethyst crystals known for the best healing properties.The mat is equipped with 7 levels 68-158F double silicon EMF free Titanium heating system. Digital controller enables to set the heating level and activate Bio Photons.