This spacer is designed to replace the three largest cogs on an HG‑spec 10‑speed cassette, allowing users to convert a 10‑speed mountain bike drivetrain into a 7‑speed DH setup without modifying the original 10‑speed rear derailleur, shifter, or chain.

It’s important to note that the original 10‑speed cassette must feature a design where the three largest cogs—such as those found in models like HG81‑10 or M771‑10—are configured as a single, individually removable cogset.