This bolt stop pin stops the bolt from crashing into the rear of the alloy receiver and in doing so transfers that energy to the drilled receiver holes. This abrupt transfer of energy can affect zero on scoped rifles. Repeated cycling will cause elongation of these holes and eventual damage to the receiver. The solution is to replace the plain steel pin with a durable material possessing the proper elasticity.
Installation is a breeze.
You just need a screwdriver, and in a couple of minutes you're ready to head for the range. You can feel the difference the first time you shoot it. Without a receiver, all those custom parts are just so many pieces.