This specially designed solid brass plug follower uses a spring loaded ball bearing stops to align and hold the plug follower in place while you drop in the springs and top pins. Start at the rear of the cylinder, drop a spring in, give it a shake and the spring will follow the V-shape and drop into the pin chamber. Next drop in a top pin, shake and the driver will drop in the chamber. Advance the tool to the next position and repeat the process until all chambers are reloaded. .498" diameter works with most common plug sizes.