Performance Tool W83163 Spark Plug Chaser, 10mm/14mm Go to amazon.com Related posts Top 10mm tap FeatureSizes: 10mm & 14mmNot to be used as a tap.Used to clean threads of spark plug holes of dirt and corrosion. DescriptionUsed to clean threads of spark Plug holes of dirt and corrosion. Not to be used as a tap. Sizes: 10 and 14 mm.