2013+ Focus ST Spark Plugs:

NGK Iridium One Step Colder Spark Plug for the Focus ST pn-LTR7IX-11 or 6510 Sold as a set of 4

2012+ 2.0 NA NGK Spark plugs:

NGK Iridium IX Heat Range 6 Spark Plug (LTR6IX-11) Price is for a set of 4