These plug tubes are held in with the spark plug in the cylinder head. Tubes are 6.250" long end to end, under the head to the tip 5.875" 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.