E-maxx Steering Servo Help

I've just upgraded to a Hitec 645 servo but the servo saver hole seems to big and it just rotates on the servo splines. i take it i need a different servo saver for the Hitec servo? I read another post about getting the UE saver which i will, I'm just saving some cash at the mo to get it
Do traxxas make different savers for different servos? may maxx was an ebay special so didn't get any others.

I've found the stock saver

http://www.wheelspinmodels.co.uk/sho...keyword%3D3744

but what are the two other spline things??? are these used for different type of servos??