ark plugs manufacture: 1.housing:martial ST10,nickel plated(bright or second bright) 2.insulator:95% pure alumina. 3.glazing:print before the glazing(like bosch,galzing at the 1000 degree centigrade) 4.central-electrode:copper core 5.inner sealing:conductive glass6.process method:hot 7.be controled heat range:controled 100%