The rocker arm shafts have a in them that the bolt is supposed to butt up against, locking the rocker arm shafts in place. However, the bolt hole is too , leaving a space. This space allows the shaft to rotate and hit the bolt, causing a tick. The R Lockers the space, locking the shaft from turning and striking the bolt, eliminating that annoying tick. The R Lockers also center the inner rocker cover so that it is always located in the same position eliminating different wear patterns on the rocker arm/valve and a better alignment of the pushrod in the holes. The R Lockers are tapered so that they lock themselves in and wedge the bolt/shaft in place. It is recommended to replace the rocker base gaskets. This is the gasket that goes between the Rocker Cover Inner & the head on each cylinder. Condition: Fitment: Fits All Twin Cams Note: If you ever need to remove the lockers, just use a punch and tap them out, they are usually reusable. Colour:Photo Color Material:brass Package Contents: 4x Brass Precision Tapered Bushings 2x O-Rings 1x Washer 1x Nut for installation 1x Centering Tool Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.