Buy Modify Airsoft 7mm Steel Bearing Bushings - Set of 6

Heavy duty and a nice tight fit.

I got these for my JG G36c which has a metal gearbox and gears but nylon bushings. Unless you are mechanically inclined and patient, however, I would not recommend putting these on yourself. I needed an extra pair of hands a couple times in order to get everything back into the gearbox where it belonged. These were a tight fit as well, which is good because if you are using a high torque motor or LiPo battery you don't want them moving on you anyways. I had to really push them into their sockets/holes and I don't know that they will ever be coming out.

if you don't have these, get them.

these fit perfectly into my jg g36k. the name of the game is reduced friction.and these bearings help with just that. I don't care if you buy these ones or a differant brand.just make the switch to metal bearing bushings if you want great internals.