Hitech products introduces the all new two piece design Billet Hemi 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 let you 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. Indy head Tube length measures 6.475". Also available for 392, 426 Hemi and Stage-5 Millennium heads. 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# HRS4