Fits 2013-2017 Focus ST 2.0L 4 cylinder EcoBoost engine Fits 2016-2017 Focus RS 2.3 4 cylinder EcoBoost engine Fits 2015-2017 Mustang 4 cylinder EcoBoost engine For use in engines with higher than stock cylinder combustion pressures Two heat ranges colder than the stock 2.0L/2.3L EcoBoost engine spark plug Same spark plugs that are included with Ford Performance M-9603A-FSTA Calibration kit Sold in engine sets of 4 Spark plugs gapped to 0.028-inch (0.71mm)