Material Iridium. -Platinum-alloy tipped fine wire ground electrode, with a platinum pad on the ground electrode and an Iridium pad with cross grooves on the center electrode. VSG Series / 18mm Heads: F1197GRSI, F1905GRSI, Generator Set, F2894G, F2894GRSI, F3520G, L5100GR, L5788GRSI, L7040G, L5100GRSI, L5788GR, L7042GSIE, F3521GSIE, 6BZ, 6LRZ, 6LRZB, 6MZA, 6MZR, ICK, 6NK, 6WAK, 6WAKB, NKRB, WAKR, LRORB, 140GK, 145GK, FC, 180G, 180GB, 180GKB, 185GLB, 190G, 190GLB, 195G, 195GK.