thaks people for all the replys, im gonna order one now, whats the best size to get?
Depends on what you're after.
Most of the arcade games used 3", so that is probably the most "arcade accurate" size.
Atari used those big 4-1/2 inchers, but I wouldn't recommend them for anything except the Atari sports games.
Which leaves the 2-1/4" ones.
They did ship in alot of games, and were very common in cocktails.
They are the easiest to control, for games like Centipede, because you are fighting less inertia to move/stop the ball.
For games that require you to really spin the ball, they are not quite as good (IMO) as a 3" because your hand can contact the 3" for a longer period of time on those games prior to just letting it go.