Specifications JBU'S Steel Ball Bearing Spring Guides Are A Must For Anyone Installing An Upgraded Spring In Their Version 3 Metal Gearbox. These Steel Ball Bearing Spring Guides Minimize Stress On The Gearbox, Piston, Gears And Motor. Installing This Spring Guide Also Raises The Rate Of Fire In Most AEGs By Allowing The Spring To Extend At A Smoother And Faster Speed. The Ball Bearings At The Rear Of The Spring Guide Relieve Spring Tension Build Up, Which Greatly Reduces The Chance Of Spring Breakage. This Steel Ball Bearing Spring Guide Was Crafted Using Cnc Machining And Lives Up To JBU'S High Quality Control Standards For Their After Market Performance Products.The JBU Steel Ball Bearing Spring Guide Is A Great Buy That Not Only Raises The Performance Of AEGs, But Also Protects The Gearbox By Minimizing Spring Tension. And, No Retailer Has A Better Deal On JBU Products Than TMC!Precision Manufactured To Ensure Durability And High Quality.