I was riding along a few weeks ago and noticed my gears skipping. When I checked it turns out that there was no gap between some of the cogs on my NX cassette! So it appears that I am missing a spacer. On my NX cassette the bottom 4 cogs are mounted on a spindle, the rest are mounted individually. Is there a specific sizer spacer which sites between the spindle and the next individual cog? If so what size is it because I have lost it!

I have spaced it out with some other spacers I have lying around (1.8mm ones I think) but even running 2 the gap between the spindle cogs and the next cog is very small, too small I’d say compared to the rest.

Can anyone offer any insight into my problem? Google gives me nothing.

Yes that spacer is a lot wider than the rest. Not sure the size though but from memory I’d say maybe equivalent of three spacers.