So, I bought a KH Moment crank/hub set recently from UDC to replace the Onza hub on my KH24. I built it up, and I’ve ridden it a few times already. But I just noticed that there are what look like spacer rings that didn’t come with my order. (the black rings in the attached picture) I checked my newer style KH20, and it has them. Do these rings serve any real purpose? I’m going to ask UDC to send some, but I want to make sure I haven’t wrecked what I’ve been using already.
I don’t know but my KH24 has them too.
They werent shipped withmine either, but when they came I put them in and everything was fine. Just have them come and put them in later, I rode hard for almost 4 months w/o them.
Since the ISIS axle is tapered, you’re not hurting your hub/cranks to use it without spacers. It’s more for cosmetic appeal and to keep dirt/junk out of exposed splines. I suppose if you had a really flexy frame (perhaps a N36 that you squeezed the legs in on to fit a normal width hub) it would also help keep the bearings from sliding up and down the axle.
If hubs didn’t come with them, at least once a week threads would pop up with the title "HELP!!! My cranks don’t go on all the way!!! 
".
this does remind me, before you get them, you may want to check the crank bolt tension now and again, b/c the cranks seemed to move up, causing the bolt to loosen a bit, where when the spacers are in, you tighten the crank and bolt to something solid, not the taper.
Yes you want them, the spacers keep the crank from going too far onto the hub and thus enlarging the hole in the crank, making it loose.
hey… thats what i was going to say…
It will also keep your frame from shifting around pushing your bearing around on the axle. I think this is less of a problem on the KH hub, but still could happen I would guess.