Hi. I'm looking at wheels on e-bay. I want some Mavic D521s. Most are dark gray, but some are silver. Is there a difference in performance/strength?
Also, while I'm here, Can I put a 20mm axel through a front shimano deore hub? Thanks.

cd gray slightly tougher, and £10ish dearer and no not on deore.

The silver (argent) ones are french the gray ones american?

gray ones (mavic 521 cd) are hard anodised, silver ones are not. gray ones resist scratches a bit. i've got some btw.

Cheers
About the 20mm axel then. If I want to use some forks that come with that , I need to make sure I have a special hub, like a Hope or something?

yes a hope will be fine 😀

The grey ones look nicer, had two pairs, v tough. Good stuff. The new ones are black with yellow decals if ye did'nt know, just as good with a more 'sick' look. ahem

A hope xc will not be ok though… I think, they are only compatible with quick release…