Rear sprocket

I'm changing the rear sprocket on my (new to me) 2001 -500S, and am confused about the design of the sprocket.

I've done a search about this, but have seen no advice about the rivetted on flange and "damper" thingy. Doing a market search for a replacement, seems to suggest that other than a genuine Honda sprocket- if available- most are plain types.

Any advice?

Many thanks.

The OEM one had the rubber on it to help prevent noise, as does the front.
None of the replacements really have this- jt do one for the front but that's about it really.

Thanks James, that's good enough for me. I'd been wondering whether it was maybe to do with noise.