Wattsy, what hub is it?

Freehubs for Shimano 8 & 9 speed will do 10 speed with a spacer added (comes with a 10sp cassette.) 10 speed specific hubs (like the Dura Ace wheels) will only do 10sp as they are too narrow for 9sp.

Mavic hubs need a spacer for 8sp & 9sp (comes with the hub) and for 10sp you need the Mavic spacer plus the Shimano spacer.

Correct me anyone if I am wrong.