One of the best, and sometimes missed tuning tricks is not to just optimize your initial timing, but to bring in timing advance more quickly than the stock distributor can allow. Bringing timing more quickly than stock can provide substantial increases in both torque and horsepower depending on your combination.This is done by changing the springs under the cap. This kit includes three sets of springs which can be used in different combinations to provide full advance between 2000 to 2800 RPM (revolutions per minute). Use lighter springs to bring the advance more quickly, and heavier springs to bring it in more slowly. Brass stop bushing is designed to help limit total timing and is more durable than factory rubber bushings. Springs are color coded as follows: Light Springs - Black Medium Springs - Silver Heavy Springs - Gold