The Rocker Lockers eliminate the gap, locking the shaft from turning and striking the bolt, eliminating that annoying tick so many Harley owners experience. The Rocker Lockers also center the rocker plate so that it is always located in the same position eliminating different wear patterns on the rocker arm and valve and also provide a better alignment of the push rod in the holes. The Rocker Lockers are tapered so that they lock themselves in and wedge the bolt/shaft in place. However, this is a single-use design. Once the rocker shafts have been removed you need a new set of Rocker Lockers. Easy to install with the included Teflon centering tool and step-by-step installation instructions. One kit serves a front and a rear cylinder head.