This uniquely designed hydraulic primary chain tensioner kit completely outdates the mechanical stock type chain tensioner. This kit improves shifting performance, reduces noise, extends primary chain life, and reduces vibrations caused by the primary chain drastically. This hydraulic plunger does not require a feed line, as your primary oil "fills" the system automatically. The tensioner is designed to automatically and continuously self adjust the primary chain tension, even during acceleration and deceleration. Kit fits all Big Twin models from 1965-2006, except 2006 Dyna, and comes complete with easy to follow fitting instructions. Installing this kit is very easy and does not require any special tools or modifications.