This is a base extension for the swivel mounts    It is an addon on piece and you must also purchase a swivel mount   

iit is the full width of the mount

****While 3D printing provides really good production quality parts, there are often imperfections that may be found on the prints. These do not impair the function and rarely affect the aesthetics. But if your not happy with the quality, please text, email, or message me before leaving a review.