These are the AC Delco Iridium spark plugs that come standard on the new C6 Corvette ZR1 and Z06. They are a bi metal premium plug that are a mid heat range cooler than standard LSx plugs. This makes them idea for any 2005+ LSx performance application such has forced induction, or nitrous where a cooler plug is idea. Plugs are sold in sets of 8, and come gapped to .040. AC Delco plug PT# is 41-104.