Many older Mack Volvo and International Trucks, 4-3/8" ID - 8 Threads per Inch, Locking Fuel Cap FTA-C-04
Cap Assy Alum 4.0-8 NPSL 190°F Thermal W/ Pressure Relief Locking 12.00 Chain & 8.35 Bail W/ 'DIESEL ONLY KEEP CLEAN' (tank must be vented)