Maple Leaf 6.02mm Precision Inner Barrel for AEG (229mm / 275mm / 310mm / 370mm)6. 02mm bore diameter increases FPS over stock setup. Increased bore consistency increases accuracy consistency. Compatible with standard Tokyo Marui spec AEG. These barrels have a special cut window that works better with the Maple Leaf range of buckings than other brand barrels! (Please note to use AEG spec buckings and NOT GBB spec buckings)