Hitech products introduces the all new two piece design Billet Hemi 392 Mickey Thompson spark plug tubes. These billet tubes will never need to be replaced again. Our Billet Hemi tubes are made with heavy gauge .055? wall thickness, and are machined in America using American Made 6061 T-6 billet aluminum. In addition, the threaded tube insert ends are made from steel. These Hitech steel insert ends allows you to service your engine without damaging your tubes. Factory and other aftermarket companies manufacture their tubes using spun aluminum or the deep drawn method which yields to thinner .035? wall thickness tubes that easily distort and dent. Note: tube length should be measured from the O-ring seat to the very end of the tube. Hemi head Stock length Tube measures 5.975". Tubes fit all Factory and aftermarket steel and aluminum Hemi heads. First Generation Hemi 1951 to 1958, 331, 354, 392 engines. Second Generation Hemi 1964 to 1971, and all newer Factory 426, 472, 528 crate Hemi engines. Tubes are measured from the O-ring seat area of the tube to bottom of tube. Don't forget to check out the all new awesome looking Hitech billet spark plug decorative covers. Part# HRS9