Billet Hemi Fathead/Musclehead spark plug tube. These plug tubes are designed to be used with the Williams fabricated valve covers and are made from solid billet alum. ends with steel centers to provide the most clearance when being used with Manton Hemi rocker arm assm's. These allow the racer to pull the valve covers off without pulling the spark plugs out of the cylinder heads. Tubes are 8.00" long end to end, under the head to the tip 7.70" and are sold separate. Plug tube diameter is 1.255" where it registers in the head and valve cover and the actual tube portion is 1.180" in diameter. Fits Williams, Moroso, BAE, valve covers using BAE, Manton or T&D rocker arms on BAE, Noonan, Total Flow, MBE cylinder heads.