The fixed vertical ring transmits short tugs and tightens the jerks. Then let it sink back down without maintaining continuous tension: the pause keeps the jig in the search zone.
The streamlined sinker accompanies this slow descent, while the feathers serve as a reference point between the final retrieves. This 17.5-gram version is used when the current allows for a controllable drift. If the drift becomes too strong, change the fishing angle or the type of descent.