Drag Specialties Pop-Up Low-Profile Gas Cap For Harley Billet aluminum construction that is available in a polished chrome or wrinkle black finish. The fit is nearly flush when closed and then it opens easily with just a quarter-turn of the center of cap. Features: Available vented or non-vented versions 2.36 outside diameter Sold each Cap Styles: Vented caps are usually used on gas tanks with one cap or on the right side of tanks with two caps Non-vented caps are usually used on the left side of tanks with two caps