The SRC 8MM Complete Gearbox for MK36is the best way to upgrade your gearbox to shoot high a FPS, ~400. The purpose of the 8mm ball bearings is to reduce the friction put on the gears fulcrum while spinning. Don't make the mistake of thinking the only way your gears can break is at the teeth. High power springs with mediocre bushings or bearings can break the gears at the stem. A break at the stem is potentially more dangerous to the gearbox than just a few teeth breaking off. The SRC 8mm Complete Gearbox is designed to prevent damage to the gears and to prevent gearbox failure due to high stress. Stop worrying about which parts are compatible with what, or how to shim. SRC has done all the hard work for you.
Material: Reinforced Steel
Design: Version 3 MK36 AEG
Package Includes: Complete Gearbox
Airsoft GI recommends professional installation for this product.
When i got it it was easy installation and no problems.
Scares your enemies because you shoot so fast
Came w/ m120 spring not installed so if you install you need to reinforce everything or it will break i shot it with the m 120 inside and it broke the air nozzle and piston and one of the gears nobs cracked so i would advise to keep this the way it is and now uprade with the m 120 spring just keep it the way you get it and you will love it.