Can anyone explain to me what side effects are?
It is an axle system. Rather than an axle hole being drilled into the yoyo, there is a bigger hole, to fit a piece that has an axle hole in it. The outside of these pieces are different shapes/weights. This, will give you a side effect. They also have o-rings to keep them tight in the yoyo. Here is a diagram, and it pops in the yoyo(They are meant to change weights, and adding features like legos.here is a pic, and remember it is hollow and threaded to allow the identical one on the other side of the yoyo to screw into it.
And here is the side with an axle http://i893.photobucket.com/albums/ac132/throwgoon/IMG_8030.jpg
And notice the holes in this yoyo(It is a one drop 54 w/ side effects) these are where the se’s fithttp://lh3.ggpht.com/_PpMEVvqsevk/TPh7iZ3NMBI/AAAAAAAAJhU/X-5Z-g-dqqo/s800/IMG_3881.JPG
Heh, two identical threads in one day. This one has pictures, though, which is handy.
Sorry , had I known I would have posted in the other, I guess they can be merged?