NGK SILKGR9A7EG / 91731 Iridium Spark Plug Fits Porsche 06M905606D / 98790560600 With the smallest tip diameter available, OE Iridium spark plugs provide superior ignitability & long service life. The iridium/platinum surfaces ensure a slow wear rate, providing stable idle & superior anti-fouling. Laser-welded iridium center electrode tip Platinum disc welded to backside of ground electrode provides long life Trivalent metal plating for superior anti-corrosion & anti-seizing Faster starts & quicker acceleration Better fuel economy & lower emissions Best OEM Iridium spark plug available