To install, you need to remove the old cover and screw the adapter into the neck of the tank, from above to install the lid. There are adapters with right and left thread. Do not forget to indicate with which thread direction you want the cover.
In the photo I showed you about how it will look on the tank. The item "Custom HandMade Hammer Gas tank cap cover Harley Davidson Bobber Chopper" is in sale since Saturday, May 29, 2021. This item is in the category "eBay Motors\Parts & Accessories\Motorcycle Parts\Body & Frame\Gas Tanks". The seller is "garage_nishtyaki" and is located in Energodar. This item can be shipped worldwide.