Important upgrade part for your AEG 
Suitable for AEG gearbox Ver.3.
Steel Made ball bearing spring guide.
To replace the original stock spring guide of airsoft AEG.
This spring guide with ball bearing is designed to minimize the load for the motor caused by the spring tension.
It also makes spring effectively spring back.
Backstop is specially equipped with nine ball bearing to prevent spring tension build-up during full auto.
It greatly reduces the risk of spring breakage.