Fits 2008 and newer 3V heads requiring the 12 mm thread For use in engines with higher than stock cylinder combustion pressures or sustained high rpm. One heat range colder than the stock Mustang GT and 5.4L-3V truck engine spark plugs Sold in engine sets of 8 Use M-12405-3V0 spark plugs for early style 2005-2008 3V heads NOTES: 2008 engines with late style 12 mm spark plugs can be identified by coil engineering number 8L3E 2005-2008 engines with early style 16 mm "High Thread" design spark plugs can be identified by coil engineering number 3L3E part number All 2009-2010 engines use 12 mm spark plugs