Cassette spacers solve a simple problem: the gap between your freehub body and the cassette lockring needs to be just right, or the cassette won't seat properly. The Low Spacer from Shimano's CS-7800 Dura-Ace series handles specific hub configurations where the standard spacer setup doesn't work.

This spacer comes into play when you're mounting a CS-7800 10-speed cassette and the lockring won't tighten correctly against the smallest cog, or when there's play in the cassette stack even with the lockring fully torqued. The low spacer sits behind the cassette on the freehub body, taking up the difference in freehub length that varies between wheel manufacturers and even between hub generations from the same brand.

Shimano designed the 7800 series around 10-speed spacing, and the freehub body dimensions from that era don't always match what you'll find on newer wheels. If you're running a wheelset that came spec'd for 11-speed but want to use your Dura-Ace 7800 cassette, this spacer fills the extra length. The same applies when swapping wheels between bikes or when replacing a hub that had slightly different tolerances than the original.... Read More