These universal filler caps are meant to be used for either gas tank or oil tanks on custom motorcycles, hot rods, or anything else. Lowbrow filler caps fit the maxim 'form follows function'; they are all business. Machined out of solid brass, these non-vented caps are 1-5/16"-12 thread and the Buna-N O-ring seal is gas and oil resistant and keeps your fluids contained, leak-free. Lowbrow filler caps fit our weld-in or for custom applications, as well as Cycle Standard, Mooneyes & British Standard brand . Made in Ohio, USA.