Well, you COULD buy these gears, but you still have to install and shims, so it would do little for you other than increase your cost significantly. You'd have kickass gears, but you'd still have to shim them yourself.
Personally, I went for Modify high torque modular gear set in my TM M4, and will probably get a regular ratio set for the JG sometime in the future. Takes any guesswork out of shimming, since the whole unit is pre-mounted and pre-shimmed. You just install the metal bushings, install the gears, and you're good to go. These gears are excellent. They move nice and smoothly, there's no play, and they're fairly silent too. It's made a huge difference in the sound of my gun. I don't hear whining anymore, just the crisp POP POP POP of the piston. However, they're still $80, so they're not cheap.