Campagnolo spline pattern
 

I'm watching a couple of 9-speed cassettes on Ebay, both 12-21. But I'm confused: why are the spline patterns different for them?

This one looks like the freehub body that I have:

http://i81.photobucket.com/albums/j2...ssette9_02.jpg

But this one has just four splines:

http://i81.photobucket.com/albums/j2...ssette9_01.jpg

Question: would the one with four splines fit on a "standard" 9/10-speed freehub body? Or what's going on here?

You will need to try it to see. The older free hub body 9 spd is different than the 9/10.