If you're looking to adapt your Mercury wheels to handle a different make/model of cassette cogs - this is the right spot. You're also in the right spot if you've put some miles on your wheels and you're ready to grab a fresh freehub of the same type.
To order a replacement, you'll need to know a little about the drivetrain on your bicycle and the specific hub used on your wheel.
The Hub Model # must match your hubs or the freehub body will not fit correctly.
To ensure the correct cassette body is provided, please use this link to determine your hub model: https://mercury.zendesk.com/hc/en-us/articles/360041400214-MERCURY-HUB-VISUAL-IDENTIFICATION