These plugs are typically found in the 4.0T RS cars such as the RS7, S7, S6 & S8. Produced by NGK, these plugs feature an iridium tip for a longer life span. 

Why Run these plugs?

 Is your car tuned? If so, you have increased the heat within your cylinders. This increased heat can cause some issues when pushing your car to the limit. The biggest problem is detonation which is caused by excessive heat in the cylinder. 

What do they do? 

These plugs are a step colder meaning they will cool off faster than your stock plugs. This is important on tuned vehicles as it helps prevent excessive heat which can cause detonation.