It helps eliminate ball break.
You have to transfer the plug anchor, return spring, bolt anchor, pull pin spring and pull pin ball bearing. Also, it was kinda difficult to order becuase of the system that you have to go through to order it, it took a while to order. Besides that, there is nothing bad about this bolt.
It is needed upgrade for anyone who buys an em-1. It greatly reduces that amount of ball breaks that you'll have while your playing. You'll thank the bolt when you playing and not having to worry about having a ball break, and not being able to shoot, because of a simple ball break.