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ICS Complete Upper Gearbox. (M130) Features?/ Application A main feature of an ICS M4 is it's two piece gearbox. The upper gearbox can be slided out and replaced in the middle of battler within a minute or two. -Having an extra gearbox is almost like having a spare gun. Piston, Piston head and tappet plate are consider wear and tear parts that requires replacements every once a while. When somethings goes out in the middle of training session, most of the time the A.E.G. will need to be put away because repair will take about a hour with the parts available. With ICS series M4, you can carry a spare gearbox and simply swap it out in the middle of the game and be ready to go.) -A lot of players play indoor and outdoor. With a spare gearbox, you can basically meet the velocity requirement for both in minutes. (Have a M100 spring in one for indoor and have a M120 spring in another gearbox for outdoor gaming!) Complete tune up kit includes: -ICS M4 Metal Upper Gearbox with screws -ICS Aluminum full teeth full metal piston -ICS Version 2 reinforced nozzle -ICS MC-02 Tappet plate for ICS M4 -ICS Version 2 Ball bearing bushing with screw. -M130 Upgrade spring -Reinforced Aluminum Piston head with ball bearing -Reinforced Aluminum Cylinder head. -Reinforced Full Capacity cylinder (for all barrel length M4 and M16 series) | 
