A "cold plug" has a shorter insulator nose, which minimizes the amount of surface area exposed to the combustion gases. Cold plugs are typically used in racing conditions because of its ability to transfer heat out of the cylinder chamber quickly. Most turbo, supercharged and nitrous oxide applications use this type of plug because of the tremendous heat they generate. A colder plug can also minimize the risk of pre-ignition and detonation, however if the plug is to cold there is risk of fouling during extended periods of idling and low-speed operation. PRICE IS PER PLUG YOU WILL NEED 4 PLUGS FOR A WRX OR STI