45mm. Real pure shungite contains quartz and pyrite banding throughout a lattice of extremely small nano carbon molecular chains. The quartz and pyrite banding are what provides the EMF shielding mechanism as the bands become excited by the earth's natural magnetic field. The natural molecular excitation creates the conductive capacity of shungite shown in the video which distributes through the entire carbon structure of the stone. When the battery touches the real natural shungite stone, the circuit completes and the light turns on! Drape this pendant over little fluffy or little Billy or anyone else you want to protect from EMF pollution! Great for also hanging over sources of high EMF pollution like WIFI routers, Smart meters, TVs, computers and more! Check out the video above of the Pure Shungite absorbing EMF radiation from a WIFI rounter!