The performance of your weapon is one of the main factors responsible for combat effectiveness. The compression and stability of the mechanism depends on the details of the gearbox of the AEG, therefore, especially with high tuning, it is better to replace the walls with more durable ones.   

The walls of the Gearbox from Bullgear are suitable for airsoft versions of the PKM and M249. These walls have greater strength, they withstand any tuning and provide better fixation of the entire mechanism.   

The design of the walls implies the use of 9mm bearings (not included). Compatible with internal SHS spare parts from other manufacturers. The Gearbox walls are made of a single bar of Aluminum D16T, by milling on a high-precision CNC machine.