Internal airsoft parts are how you tune performance, fix wear and make a gun shoot straighter. This section covers gears, pistons, cylinders, springs, motors, hop-up units and rubbers, inner barrels and MOSFETs.Start with the hop-up rubber and inner barrel if accuracy is the goal. They often do more than a stronger spring. If you change springs, make sure the gun stays within your site’s FPS or joule limits. Most AEG gearbox parts follow the Version 2 or Version 3 standard, so check the version and motor axle length before ordering. Changing motors? Match it with the right battery.