Fits any 4" NPSL Neck found in the necks section. The 4" Designation is based on the ID of the neck this cap would thread into, Not the ID of Cap Across the threads or the OD of the neck.
Cap construction = Aluminum
OD of cap = 5.25"
ID of Cap Across Threads = 4.350"
Thread Pitch = 8 TPI
Thermal Relief = Yes, 190 DEG
Lanyard = Yes 10" W crossbar
Lettering = "Diesel Fuel Only Keep Clean"