"You should buy this Yoke Stem Adjusting Nut"

A yoke stem nut, also known as a center stem nut or top yoke nut, is a replacement nut for a motorcycle's steering stem tube. It can be used to replace a damaged or rusty nut, or to fit an accessory mount like a Quad Lock. Yoke stem nuts can be made from a variety of materials, including aluminum, titanium, and brass, and come in different colors. Some yoke stem nuts are designed to be lightweight and corrosion resistant.