Conductive black grain is most often used in key selection, conductivity, conductive particles in general mining injection molding for key bottom, long service life, can reach more than 5 millions of times, conductive coefficient is less than 200 ohms. is common in circular specifications and thickness of 0.4-0.6mm (0.010 "-0.015") or a key specifications vary, composite conductive black grain with stability and driving resistance and the price is reasonable.