Systema Tokyo Marui PSG-1 AEG Taper Spring 300%

300% spring for PSG1 allows you to crank out 450fps+ of power. But the original stock gears will not generate enough torque to compress this spring, so this upgrade must be coupled together with high torque gears. We recommend this spring as a backup replacement spring after you install the Systema FTK upgrade for PSG-1 : FTK-12. Actual results depend on barrel length, workmanship, air nozzle seal, and many other factors.
Please check AEG Spring Comparison Chart from http://www.airsoftcanada.com