This dummy gas cap matches the vented, pop-up gas caps. On Harleys with two fillers on the gas tank, this cap is for the left-hand side, on models that accept a dummy (non-functional) gas cap.

This larger diameter pop up cap has a 2.75″ diameter trim ring (the largest diameter section that lays flat against the gas tank). This ensures that the weld seam on the gas tank filler bung is fully covered. On Harley-Davidson motorcycles 2018 and later this bung size changed, and the trim ring on the smaller diameter (2.35″) pop-up caps doesn’t fully cover it.