Where do the spacers on 12-speed Shimano cassettes go?

Shimano 12-speed Dura-Ace, Ultegra, 105 and GRX cassettes come with two different spacers between the cassette sprockets.

If you've taken your cassette apart and have mixed up the spacers, getting them back on in the correct order is crucial.

Which spacer goes where?

You can usually tell which spacer goes where by looking at the cassette sprockets. The sprockets with a larger ridge interface with the thin spacers, and the sprockets (or cogs) with next to no ridge go with the thicker spacers.

If you prefer a schematic, take a look at the exploded views below:

Dura-Ace R9200 cassette spacers

The 11-30T Dura-Ace cassette has two 1.95mm spacers and one 0.95mm spacer. The 11-34 Dura-Ace cassette has one of each spacer.

Ultegra R8100 / R8101 cassette spacers

Just like its more expensive DA sibling, the 11-30T Ultegra cassette has two 1.95mm spacers and one 0.95mm spacer. The 11-34 Ultegra cassette has one of each spacer.

105 R7100 / HG700 cassette spacers

Both the 11-34 and the 11-36 cassettes have three 1.95mm spacers and one 0.95mm spacer.