There are two designs for you to choose ；

This reinforced spring rail replaces Airsoft AEG's original stock spring rail for durability

Spring guides with ball bearings designed to minimize motor load caused by spring tension

It is especially important to upgrade the AEG; make the spring rebound effectively

The backstop is specially equipped with EIGHT ball bearings to prevent

The spring tension is accumulated in the fully automatic shooting mode. It greatly reduces the risk of spring break

For Airsoft AEG Version 2 /3 Gearbox