moesaxton
really? do you really need to ask? it says on the box in small print (tested with .12 gram bbs) so yes, use .20 grammers. they make it say 487 fps so it seems amazing when they are distorting the facts. .20 gram bbs are standard for fps readings

Mo
Ultrasonic .12g. Half the weight so they go faster. Not as accurate but when I use them, the go much faster. My gun is meant to use .2g. Works just fine with .12g. You can buy these really cheap ones, great quality. I bought mine from this guy too.

SuperM
For an AEG I would recommend 0.2g or heavier BB's. They should be good quality, with no seam marks and polished (slightly shiny). Remember that heavier BB's like 0.23g or 0.25g will be more accurate, but the velocity will be slower. I would recommend the Airsoft Elite Precision 0.23g 2500 BB's . You can check out the performance levels of different weights of BB's on the following link: Get it at Airsplat! They have great service, really fast shipping and the best prices online - GUARANTEED!!